I am flying to Zurich this September with a decent layover in Toronto. As a US citizen, do I have to go through Immigration AND retrieve my checked bag for customs in Toronto before proceeding? Its not an issue coming BACK, as I layover in Newark.

No. If you have an international connection & you stay in the international section of the terminal for your flight, you will not have to clear immigration. After you deplane, keep your eyes open for staff that will direct you to international connections. Don't follow the hordes towards customs . . .

Ian

There will BE a staff member to direct you after you de-plane. BUT, how LONG is that "decent" layover because that can make a difference in terms of your being allowed to transit to the correct concourse. I know that is what happened to us about a year ago when we had a five-hour layover.

The issue ISN'T what passport you're carrying: it's which airline(s) you're flying on and whether the booking is all on one ticket.

Under a number of circumstances, a traveller arriving from the US and going on to a destination outside North America DOES need to present herself to Canadian immigration. In my experience inflight staff on US-based airlines are utterly unreliable about this, though checkin staff at your US airport are probably better briefed.

There's a guide at the Peason airport site that takes you through the range of possible processes (http://www.torontopearson.com/Connecting.aspx#)

Use it.

Yeah! Thank you flanneruk...exactly what I was looking for.
I am flying aircanada into and out of Toronto, one ticket, two hour layover. I've never been through YYZ before, so this really helps!