The single-cell gel electrophoretic (SCGE) technique for detecting the presence of DNA strand breaks and alkali-labile damage in individual cells was used to examine the effect on newborn infants of maternal exposure to cigarette smoke. The levels of DNA damage in the lymphocytes of 21 newborns of mothers with different smoking habits were compared to those in 10 newborn infants whose mothers had never smoked and 8 newborns whose mothers were passively exposed for at least 40 h per week in the workplace and home. DNA damage was undetected in lymphocytes of newborns of passively exposed mothers or newborns with mothers of low smoking habit by conditions allowing 40 min DNA unwinding and 40 min electrophoresis. Presumably longer times were needed for lower levels of damage to be detected by SCGE. The mean length of DNA migration in lymphocytes between the newborns of smoking mothers did not show any significance but the percentage of damaged cells increased with the frequency of smoking when assessed by non-parametric Mann-Whitney U test. The results of SCGE were compared with our results published in the same individuals of sister-chromatid exchange (SCE) frequency. The results show similar trends with mean measures of DNA damage increasing with frequency and long history of maternal smoking. These observations encourage the application of SCGE as a sensitive and useful technique for quantitating DNA damage in individual cells.