This study was designed to investigate the effects of nicotine on in vitro embryo development at a variable duration of treatment schedule. A concomitant oxidative stress level was also evaluated. Four- to six-week-old female mice (Mus musculus) were injected (s.c.) with nico-tine (5.0 mg/kg/day) for 7, 14 or 28 consecutive days. Animals were superovulated and co-habitated overnight with fertile male at a ratio 1:1. Forty-eight hours post-coitum, blood samples of the animals were collected for manoldialdehyde (MDA) estimation. On sacrifice, ovaries including the fallopian tubes were excised. Fallopian tubes were flushed and the normal embryos were subjected to in vitro culture. Out of 783 retrieved embryos, only 61% were found normal. Nicotine increased the number of abnormal embryos (61.7 ± 9.3) as compared to controls (40.3 ± 8.1). None of the embryos formed blastocyst following nicotine treatment for 7 days. When the length of treatment was extended for 14 days, embryonic development reached only up to 8-cell stage. However, most of the embryos stopped dividing at 2-cell stage after 28 days of nicotine treatment. Plasma MDA concentration was found to be higher in all the three groups of nicotine-treated experimental mice compared to control groups. Ovarian MDA levels showed a significant difference between the groups of animals treated with nicotine for 14 days and 28 days, but not between two other treated groups, those received nicotine for 7 days and 14 days, respectively. In conclusion, the degree of im-paired development of the preimplanted embryos seems to be directly correlated with the length of nicotine treatment with a corresponding increment of oxidative stress.