The aim of this study was to investigate the effect of maternal nicotine exposure during pregnancy and lactation on the development of the lungs of the offspring as a gas- exchanger. Pregnant rats received nicotine (1 mg/kg body mass day–1) subcutaneously during gestation and lactation. Nicotine administration started one day after mating and lasted until weaning on post natal Day 21. The offspring were exposed to nicotine only via the placenta and the milk of the mother. The lung tissue of the neonates was collected on post natal Days 14, 21, 35 and 42 and prepared for morphometry. The results obtained show that maternal nicotine exposure suppressed alveolarisation in the lungs of the offspring, which resulted in a reduced internal surface area available for gas exchange. The radial alveolar count as well as the number of capillaries in the septa were also significantly lower than in the control animals. It is concluded that maternal nicotine exposure had an adverse effect on the development of the gas exchange region of the lungs of the offspring that persisted at least up to Day 42 after birth.