Two groups of female Sprague-Dawley rats (210±15 g) were fed throughout gestation one of two diets (n=12 for each diet), either control or lithium-containing (0 or 1000 ppm lithium carbonate). At parturition, half of the rats (CL) that had been fed the control diet were switched to the lithium diet, and half (LC) that had been fed the lithium diet were switched to the control diet. The remaining rats in each group were fed during lactation the same diet as during gestation (CC and LL). Dietary lithium during gestation resulted in a significant decrease in weight gain, feed intake and feed efficiency, and significantly decreased litter size, total litter weight and mean pup weight. Litters were standardized to six male pups per litter on day 1 of lactation, and after 21 days, the mean number of pups and mean pup weight (g) per standardized litter were CC 6.0, 55.2±0.8; CL 6.0, 42.1±2.9; LC 5.7, 54.4±2.1; and LL 4.8, 53.4±1.8. During lactation, lithium carbonate ingestion significantly affected the weights of both liver and kidney. Dams fed the control diet throughout gestation and lactation (group CC) had larger kidneys than the three groups (groups CL, LC and LL) ingesting lithium. The results of this study show that dietary lithium affects body weights of pregnant and lactating dams as well as growth and survival of their pups. It is proposed that these adverse effects of dietary lithium can be studied to examine the nutritional and toxicological consequences of lithium ingestion.