Three concurrent studies were conducted to determine the chronic effect of prespawning exposure to various concentrations of copper on fathead minnow reproduction. Copper was introduced into the three exposure systems to give 6-, 3-, and 0-months exposure prior to spawning. Prespawning exposure time had no significant effect on reproduction. Number of eggs produced per female decreased, however, with increase in copper concentrations. Egg production at copper concentrations of 37 micrograms/liter and higher was significantly lower (P=0.05) than in the control, but at concentrations of 24 micrograms/liter and lower it was not different. The maximum acceptable toxicant concentration (MATC) was estimated to be 32 micrograms Cu per liter, which is 0..07 of the 96 h LC50. This application factor for copper is similar to those found in other studies.