Bicycle Tutor

I have a 26" Trike made for handicapped people. It is geared with the older style 10 speed derailleur system. The problem is, the chain keeps falling off the rear sprocket. It is mainly ridden using the lowest gear but it comes off every few meters and is a real nuisance. Can anyone give me advice as to what to do.
Thanks
Neil.

Maybe the chain line is off. Take a look down the chain from the rear. It should look straight in line with the front chainring and the rear sprocket. If you have multiple gears on the back, place the chain on the middle sprocket and use that to check it out.

I will have a look at that in the morning.
Thanks.

26" inch trike 10spd? Cool, is it a recumbent or just a regular trike? I have a Schwinn Meridian that I am possibly looking into making a multi-speed. Be sweet if you could post a picture or two of it. Good luck on the chain problem. Sorry to post here Alex, just find trike fascinating