Numerous experimental models have been developed for the study of the polycystic ovarian syndrome in the rat. In the present study, the syndrome was induced by exposure to constant light. The process was evaluated during its induction and also during its reversion. The estral cycle was analyzed through the vaginal cytology; reproductive parameters were evaluated by mating, as well as the ovarian morphology. All the animals developed the syndrome after 13 weeks of permanent light. The histologic characteristics of the ovaries, at week 15, were similar to those observed in the polycystic ovarian syndrome in human and other species. After regression of the syndrome, there was not difference in any of the evaluated reproductive parameters, when compared with the control group.Numerosos modelos experimentais tem sido desenvolvimos para o estudo da sindrome do ovario policistico em ratos. No presente estudo, a sindrome foi inducida por exposicao a luz constante. O processo foi avaliado durante sua inducao e inclusive durante sua reversao. O ciclo estral foi analisado atraves de citologia vaginal; parametros reprodutivos foram avaliados por acasalamento, bem como a morfologia ovariana. Todos animais desenvolveram a sindrome depois de 13 semanas de luz permanente. As caracteristicas histologicas dos ovarios, na semana 15, foram similares aquelas observadas na sindrome do ovario policistico em humanos e outras especies. Apos a regressao da sindrome, nao houve diferenta em nenhum dos parametros reprodutivos avaliados, quando comparados com o grupo controle.Facultad de Ciencias Veterinarias