We studied the effect of maternal nicotine exposure in rats during a) gestation and lactation (G&L), and b) from the onset of the phase of rapid alveolarisation (PNE) on lung development in the offspring. Nicotine was given to the mother (1 mg/kg maternal body weight/day, subcutaneously) only, which means that the fetuses and neonates were exposed to nicotine via the placenta and/or mother’s milk only. Lung samples were collected on postnatal days 14, 21, and 42. The BW, V_L, S_a, N_a, V_alv, Tw and AWUV of the lungs were determined. The data obtained show that maternal nicotine exposure had no influence on BW and V_L of the offspring. The other parameters were also the same up to postnatal day 21. On postnatal day 42 the S_A of the control lungs was bigger than that of the nicotine exposed rats. The Valv of the control lungs was smaller than that of the nicotine exposed animals while the N_a of the control lungs was higher than that of the nicotine animals. No differences were evident between the G&L and PNE animals. Microscopic emphysema was also observed in both the G&L and PNE groups. The alveolar walls of the 14-day-old G&L rats were thicker than that of the control and PNE rats. On postnatal day 42 there were no apparent differences. From the data it  appears that the effect of nicotine exposure from the onset of alveolarisation is as detrimental to neonatal lung development as exposure during all the phases of lung development.