The hatchability of sheep gastrointestinal nematode eggs exposed to ultraviolet (UV) radiation and the activity of the hatched larvae were examined. Hatchability decreased with increasing exposure to radiation. The difference in hatchabilityof eggs irradiated for 15,30 and 60 minutes were highly significant (p < 0.01 dalpha = 3.07, 3.24 and 3.75) compared with the hatchability of the nonirradiated eggs. The life span of irradiated larvae was shortened, only 20% of those expose to UV radiation 60 minutes survive for 2 days as against 100% survival rate in the non-irradiated larvae. Batches of nematode larvae (L1) were irradiated with ultraviolet (UV) light for varying time interval to determine the influence of radiation on the transmission potential of the irradiated larvae. There was a decrease in the survival rate of the hatched free-swimming larvae that corresponded with the increasing radiation exposure time.