This paper describes effects of temperature on herpes-like virus detection in Pacific oyster Crassostrea gigas larvae held at different temperatures. Intranuclear, intracytoplasmic and extracellular viral particles were observed in velum and mantle connective tissues of oyster larvae reared at 25-26°C. In larvae held at 22-23OC, although nuclear lesions were observed, the presence of viral particles was not detected. Results were obtained for oyster larvae with 4 different parental origins. Herpesvirus infection was found in 3 of the 4 groups of oyster larvae held In the same conditions at the higher temperature.