Abstract: BACKGROUND AND AIM: In view of the follicles proliferation is sensitive to the physical and chemical stimuli, to establish the follicles culture in vitro growth system, as an efficient biological model of reproductive toxicity. MATERIALS AND METHODS: 140-160 μm preantral follicles were selected to culture in vitro for ten days, the diameter of follicles was measured each other day. The ovulation of survival follicles was induced by HCG hormone. About 16-24 hours later, the matured oocytes, germinal vesicle breakdown (GVBD) and germinal vesicle (GV) oocytes were calculated under the stereomicroscope. Chromosomal abnormalities of matured oocytes including numerical and structural aberrations were investigated and recorded. RESULTS: Total of 332 follicles were separated from ovaries of 4 female mice, the mean diameter of follicles was increased at the early culture time in vitro, then follicles grow as ‘Frangipani’, some of them formed the antral-like cavity. On the 10 day of culture, the survival rate was 95.78％ (318/332)，the rate of ovulation induced by hormone in vitro was 72.01％ (229/318)，including 11.80％ oocytes arrested at germinal vesicles stage, 39.30％ oocytes showed germinal vesicle breakdown, 47.16％ oocytes emitted the first polar body and 1.74％oocytes were parthenogenesis. The chromosomal abnormalities of matured oocytes have no significant difference comparing with that of oocytes in vitro maturation (IVM) and oocytes superovulation (IVC). CONCLUSION: The oocytes matured from preantral follicles cultured in vitro were similar to those matured from in vivo growth. Therefore, the preantralfollicles cultured in vitro growth system maybe a good testing model of reproductive toxicology or follicular developmental mechanism in vitro.

Key words: reproductive toxicology, preantral follicles, in vitro, chromosome aberrations