The current study was undertaken to investigate the presence of heat shock proteins (HSPs) in a monolayer culture of pig ovarial granulosa cells submitted to stress conditions, and to exactly define heat shock (43 deg C) after 1, 2, 4 and 6 hours. For the detection of HSPs immunocytochemical reaction with a monoclonal antiHSP70 antibody was used. The adherent granulosa cells growing in the monolayer showed the strongest reaction after 4 and 6 hours heat shock, especially when the culture was transported, after 6 hours of heat shock, into normal culture conditions (temperature of 37 deg C). A very strong positive reaction was exceptionally concentrated within the nuclei. There was a substantially weak reaction within the cytoplasm. Reaction in the control culture cells was minimized and, after 1 hour of heat shock, the presence of HSPs was also very weak. The induction of HSPs into a culture of pig ovarial granulosa cells after heat shock presents a very interesting model for the study of cellular adaptive response to external stress.