We are staying 7 nights in SML in Sept. Is it feasble to take a day trip to Monaco and if so by boat or train? thank you.

I am in SML now. I have done that route many times except I go on to Nice. I would not think of doing it as a day trip. I leave here on May 3 at around 11:30 AM and I do not get to Nice til after 4. I suppose you could get an early train and stay a couple of hours, but your entire day is basically on the train.

It would be an extremely long day trip. I would not personally consider it. We drove from San Remo to SML one time and that took quite awhile.

OK, I'LL CROSS THAT IDEA OFF MY LIST, THANK YOU VERY MUCH FOR YOUR REPLIES.
I PROBABLY SHOULDN'T PLAN ON GOING ANY FURTHER THAN CINQUE TERRA FOR A DAY TRIP FROM SML, DO YOU BOTH AGREE?
THANKS AGAIN

I agree. You could go to San Remo but it might be a bit dull. I love the hiking around Portofino and SML. There really is enough to keep you busy especially with a day trip to Cinque Terre.
Where are you staying? My favorite is the Hotel Continental. I just can't get enough of their "beach" and view.
Have fun!!