[Eva]

I remembered from chemistry class that it was bad, but I couldn't remember exactly what happened if you mixed them. I'll remember to tell that to my mother-in-law.

[HiTech RedNeck]

You get chloramines, though from household strength ammonia and bleach you don't get anything significant except in a closed area. Once years ago, when a kid with a slightly twisted mind, I poured a cup of each into a bowl in the middle of the back yard expecting it to generate a huge yellow-green cloud of noxious gas or something. The result was not even enough to smell.