Objective. To evaluate the effect of myoinositol on preimplantation mouse embryos. Material and methods. Mouse embryos were obtained from females of F1(CBAxC57Bl). Oocyte-cumulus complex were obtained and purified in several consecutive drops of medium. Embryos cultured in cleavage and blastocyst fertilization media in the presence of myoinositol or in its absence and evaluated morphologically. Results. Comparison of growth properties of IVF medium was obtained with adding composition of vitamins corresponding to culture media: DMEM, F-10, RPMI-1640, 199. It has been found that the vitamin composition of the medium RPMI-1640 significantly improves the nutritional properties of the medium. Serial analysis of all the vitamins included in the RPMI-1640 found that improving was associated with an increase in the concentration of myoinositol. Incubation was carried out in the medium with myoinositol and without it. In control media without myoinositol at day 5 of culture were observed 62±3% blastocysts (23 of 37 cells). If myoinositol was added to cleavage medium for 48 hrs, there was an increase in the blastocyst to 77±2,2% (p<0.05) (30 of 39 cells). After addition of myoinositol into the blastocyst medium only (from 48 to 120hr), the percentage of blastocysts did not differ from control - 67±3.2% (18 of 27 cells). Myoinositol added to both media provides the highest percentage - 85±2,8% (23 of 27 cells). Optimal concentration of myoinositol analyzed in range of concentrations from 10 to 35 mg/L. It was shown that the optimal concentration of myoinositol during incubation for 5 days was 25 mg/L. Embryos incubated in medium with myoinositol had higher rate of hatching on 5th day than in media without myoinositol, 91±2.2% versus 78±3.1% (p<0.05) in control. Conclusions. The presence of myoinositol resulted in both an increase in proliferation activity and developmental rate of in vitro cultured early mouse embryos. The positive effect of myoinositol at a concentration of 25 mg/L is optimal for the early embryo.