Effects of pregnancy superimposed upon a rapid phase of growth in the rat on the vitamin B-6 needs during gestation were examined. Rats were fed 1.2, 2.4, 4.8, 9.6, or 19.2 mg pyridoxine-HCl/kg diet from weaning. Some animals from each dietary treatment were mated at 55 (P-55) and 115 (P-115) days of age; others of the same ages served as nonpregnant controls. Analyses were made on day 21 of gestation. Excepting the 1.2-mg diet treatment, maternal weight gains during gestation were greater for P-55 groups compared with gains of the P-115 groups, possibly reflecting maternal growth. Both maternal weight gains and fetal weights were less for the 1.2-mg, P-55 group; otherwise reproductive performance was similar among the groups. On the basis of stimulation of erythrocyte alanine aminotransferase activity by pyridoxal phosphate added in vitro, the needs in all pregnant and nonpregnant groups were met by 2.4 mg pyridoxine/kg diet. However, on the basis of vitamin B-6 saturation of tissues, the pyridoxine needs were 9.6 mg/kg diet for young growing animals and 4.8 mg/kg diet for older animals in which growth had almost ceased. The needs for both young and older pregnant animals possibly exceeded 19.2 mg pyridoxine/kg diet for vitamin B-6 saturation of maternal liver, fetus, and fetal brain. Pregnancy superimposed upon a rapid phase of growth in conjunction with a restricted intake of pyridoxine resulted in low values for most parameters used in the assessments compared with values for animals fed the same vitamin level but mated after growth velocity had diminished.