To assess the impact of long‐term feeding of fungicides on sperm quality, mice were fed a daily diet containing a mixture of maneb and zineb, at concentrations of 30, 300, and 3000 ppm, respectively. Employing epididymal sperm suspended in a medium permitting in vitro capacitation, the intracellular free Ca2+concentration, [Ca2+]i, was determined with a fluorescent Ca2+indicator, Fura‐2. Regardless of the fungicide dosages applied, [Ca2+]i was about 50 percent higher in treated animals relative to a value of 123 nM [Ca2+]i in the control group. Fungicide‐treated mice were mated to mature, non‐treated females; as in the control, the litter sizes were the same. In conclusion, the observed elevation in [Ca2+]i seems to reflect cellular adaptation responses to toxic stress at moderate fungicide doses.