Influence of temperature on viability of Cryptosporidium parvum oocysts originally isolated from calves faeces. Cryptosporidium parvum oocysts originally isolated from calves faeces were submitted to various temperatures at different times in order to estimate their viability and infectivity. The results of this study showed that cryptosporidia oocysts aren’t viable after 2 months if they are kept at +4 °C and after 3 weeks at 18-22 °C. However, the duration of viability of oocysts is increased until 6 and 1 month if they are maintained in addition with potassium dichromate (K2Cr2O) (2,5%) at +4 °C and 18-22 °C respectivelly. Contrary, the oocysts lose their infectivity when they are stored at -20 °C after 1 hour, -10 °C and 0 °C after 12 hours of incubation (with or without the solution of conservation), 23 °C after 3 weeks, 34 °C after 2 weeks, 40 °C after 4 days, 45 and 50 °C after 45 minutes, 51 and 55 °C after 35 minutes, 60 °C after 25 minutes, 65 °C after 15 minutes, 70 °C after 5 minutes and 75 °C after 3 minutes. However, the wet temperature 50 and 55 °C are effectif against cryptosporidia oocysts after 60 and 30 minutes of incubation respectively. The oocysts lose their normal morphology after 24 hours at -10 °C and 9 months at +4 °C when they are stored in potassium dichromate. On the other hand, no oocysts are morphologicaly damaged for other periods of exposure even when the latest are exposed in higher temperatures 70 and 75 °C.