My husband and I are travelling for the first time to London and Paris the last 2 weeks of October. According to our Fodors Guide, the attire in the evening is fairly "dressed up" for casual dining in Paris. We are in our late fifties and will grudgingly leave the jeans and athletic shoes at home.

Is a pantsuit ok for evenings: theater, dining, etc? Also, is a long sleeve shirt and suede or wool coat for my husband ok, or is a tie and/or jacket required?
Advice, anyone?

We most often go to Paris in Oct or Nov. It is fairly cool and sometimes wet at that time of year. A pantsuit is perfect for your more dressy evenings, more casual nights you can just wear trousers and a sweater. If you are going to the Opera House, do dress up, you will love the whole experience!
Your husband will be fine in a jacket and shirt, ties will only be required at a 5*, very posh restaurant. Although, mine wore a tie and jacket when we ate at Le Violin D'Ingres and Helene Darozze.
I think calling it "dressed up" is just as you say-leaving the jeans and sneakers at home
You will have such a wonderful time, and two weeks! Lucky you~

When we were there last summer, we saw many Europeans in jeans and athletic shoes...wear what is comfortable that you already own, and that is broken in.

London has the most off the wall of dressing, anything goes. Have fun. A tie you can tuck in a shoe in baggage in case he needs it. Most restaurants in Paris have gotton very relaxed in that.

Fodors is wrong, casual dining in Paris is not "fairly dressed up". It is casual. However, they may be writing to those who wear jeans and sneakers out in the evening, so anything else is called dressed up. However, unlike certain areas or restaurants in the US, casual does not mean sloppy jeans and athletic shoes and T-shirts or sweatshirts, at least not on people in their late fifties. Not to belabor the obvious, but there is a big difference between light blue, somewhat baggy farmer-style or discount-store blue jeans and athletic shoes in comparison to well-fitting, tailored jeans with interesting jewelry and belt, with a more stylish shoe and a top such as a linen or silk blouse. Even at the rather casual end of jeans and casual shoes, you may see those in their 20s wearing this but not adults in their late fifties, at least not out to dinner.

I'm not as rigid about this as some and I may wear black jeans with a nice leather slide or dressy loafer with a leather and silver belt and silk sweater or something like that out to any casual cafe or brasserie in Paris, but I have never once seen a local woman in her 50s at a restaurant in Paris in blue jeans and sneakers.

I don't own a pantsuit, although there are some nice ones, but I wouldn't ever take one traveling because they are so bulky. A nice pair of black slacks or skirt with various tops would be more versatile and easier to pack, it seems to me. A nice pantsuit would be okay, but not something you'd wear around sightseeing during the day, probably. Actually, theater is London is pretty casual and you can wear almost anything for that.

It takes almost no room to pack a tie, but I would think your husband could get by almost anywhere with what you describe, except for fine restaurants.

We are in these two cities every spring and have relatives in Paris and I know plenty about how the locals dress there. Our French family frequently wear jeans and athletic shoes---but on weekends or when going out to the country.

Casual in London means just about anything these days, but I would most certainly leave the jeans and athletic shoes home (the white ones anyway). London theater is anything goes, however I like to wear black pants, a blouse or t-top/sweater and blazer. A nice blazer will go with lots of things and dark pants are the best. Again, tho you will see almost everything from real formal wear to really scrungy. London theater attracts a lot of locals who come directly from work, they will be in business clothes. Your husband does not need a jacket/suit/tie .. trust me on that! A decent looking shirt and pants will do just fine and he will look fine.

Incidentally, I've worn jeans in both cities many times--the nice kind that you can dress up with a sweater/blazer, scarf. You won't see any older French women wearing jeans but you will see lots of younger ones on the weekends or their free time and they can look smashing in them. The right jacket, scarf, etc. can make jeans look elegant (really!). However, most American tourists don't look that great in jeans as Christina said so it's better to stick to black or brown pant or navy blue. You will see all sorts of tourists in Paris and they will all be dressed however they want, but you cannot go wrong wearing comfortable clothes and looking nice.

I would not bother with a pantsuit, I am a real fan of blazers and you can mix and match them, dressing them up and down.

As for shoes .. a black athletic shoe is certainly OK for sightseeing if there is a brand you particularly are comfortable with. I wear a brand called Propet myself. I have a foot problem and have custom inserts and these are the the only shoes I can walk all over cities in with no pain (go figure, they cost $39 but the custom orthodics were $375!!)
With the right pants length the black athletic shoes barely show anyway. My husband favors black pants while in Europe also and he too has black athletic shoes for all the walking around. When your feet hurt you are miserable so find something comfortable and stick with it when you know you are going to walk a lot.

Fodor's guide on clothes is a little out of touch.