Introduction: Opioids and morphine are increasingly abused in modern societies, especially in recent years. Therefore, the present study was designed to evaluate the effects of morphine depen-dency on rats’ sexual and maternal behaviors, birth rate, sex ratio and the rate of stillbirths. Materials & Methods: Adult male and female rats were allocated into treatment and control groups. The treatment group was sub-divided into two morphine-dependent groups, group I) consisting of a number of male couples and group II) of both parents. Morphine dependency was induced by gradual administration of oral morphine with a final dose of 0.4 mg/ml dispensed in drinking water for 14 days. Morphine dependency was confirmed by the observation of changes induced by naloxane administration. Sexual behavior was determined by vaginal plague obser-vation. Weight gain during pregnancy, rate of stillbirths, sex ratio, and maternity behavior (Caring for the neonates or eating them) were assessed in the groups. For statistical tests, one-way ANOVA with its non-parametric equivalent and for comparing means, 2 were used while employing SPSS software, version 13, for statistical analysis. The level of significance was regarded as p<0.05. Results: A non-significant decline in sexual tendency was observed in groups I (60%) and II (67%), compared to the control group (80%). In the control group, 69% of all matings resulted in delivery compared to 39% and 38% in groups I and II respectively (p<0.05). Weight gain in groups I, II and the controls were 46±38, 28±28 and 62±33 grams respectively. Weight gain difference between the control group and group II was statistically significant (p<0.05). Sex ratio was 1.17, 1 and 1.57 in groups I, II and the controls, respectively. No stillbirths were seen in group I, while the rate of stillbirth in group II (67%) was statistically significant (p<0.001); one stillbirth was also seen in the control group. The rate of pup cannibalism in female rats on group II (37%) was significantly higher (p<0.001) than group I and the controls. Conclusion: Morphine dependency neither had effects on sex drive nor on fertilizing capacity in male or female rats but it increased the rate of pseudo-pregnancy. Morphine also increased the rate of stillbirths but it adversely affected maternal weight gain during pregnancy. Maternal beha-vior was highly affected by morphine dependency as well.