Serum human placental lactogen (HPL) levels were measured in the last trimester of pregnancy in 16 mothers who delivered small-for-gestational-age babies. Only 3 patients had levels which were below the normal range, while 4 others had levels close to the lower limit of the normal range. The finding of a normal serum HPL level therefore does not exclude the possibility of intra-uterine fetal growth retardation. No correlation was found between serum HPL levels at 37-39 weeks and infant or placental weights in full-term normal deliveries.