You might have a plant infected with Black Sigatoka a/k/a black leaf streak. You can learn more about this disease and compare the appearance of your plant to others harmed by the disease at:

http://www.ctahr.hawaii.edu/nelsons/banana/BLS/BananaBlackLeafStreak1.htm

A good quality fungicide should help you to remedy the problem. Also, make sure your pot allows for adequate drainage. Good luck!

Here is a link that might be useful: Black Leaf Streak

Thanks, I'm not sure that's it. What's on my plant looks more wet and it has not spread onto the leaf. It's just staying in that one spot and seems to be just spreading to the parts underneath that area. I might can get a picture.

Ok. Then it could be rot from overwatering or from sitting in a pot with soil that is too dense and not draining adequately, or from being in a pot that is much too large for the size of your plant, thereby holding a lot of excess moisture. You may want to re-pot it, inspect the corm and roots for signs of rot, and include some course material, i.e., orchid mix, perlite, etc., to help promote good drainage.

Oh, I've probably got it in a pot that is too big. I'll check the corm. Crossing my fingers it is okay. I really appreciate your help! Maybe it will have a chance of survival now.

Yippeee!!! Thank you, thank you, thank you tropicallawyer! It is doing much better. I checked the corm (which is still very small) and it was good. I cut off the brown squishy spot and put it in a smaller pot. It is growing happily and the brown spot does not look like it's coming back.

Thanks for the disease pictures link tropicallawyer.
I am a novice banana grower and just have 2 small plants.
Both have brown patches on the leaves.
I didn't think they looked diseased, but have been searching on the internet for a while, to try to find the cause/disease.
And was getting worried, seeing things like black leaf streak etc.
Then I saw a picture and description, in your link, that was a perfect match -

"Figure 4. On some varieties such as Cavendish types, leaves of young banana suckers naturally have maroon- colored blotches (above) that should not be mistaken for symptoms of black leaf streak disease. These blotches are naturally occurring on young plants and are not present on leaves of older plants"

What a relief !

14 years later and this helped me too! Thank you guys for being the saviour of my