I'm making a monostable using a 555 timer IC, and when I press a button to make my trigger go low, pin 3 comes on but stays on and doesn't come off. As I said, I have made sure that my input to pin 2 is normally high and goes low when the button is pressed (and goes high again when it is released); are there any other potential causes of this happening? My resistor and capacitor values are way too small for this to be due to the normal operation of the monostable.

I'm using a 9v power supply on a breadboard, if that helps at all.

 

Post your circuit diagram.

 

A schematic is best, but at least post the values of R1 C1.