Emphysema is characterised by a loss of alveolar structure, as reflected in elastic recoil and gas exchange. As fibroblasts play a key role in the maintenance of structure, the current authors hypothesised that their proliferation might be constitutively impaired in lung emphysema. Using explant cultures, lung fibroblasts were obtained from resected lungs of 10 patients with emphysema (median forced expiratory volume in one second (FEV1) 40% predicted) and 10 control patients (FEV1, 95% pred). The doubling time (DT) was measured over 4 days under standard conditions (10% foetal calf serum) prior and after cryopreservation. Additionally, in seven samples per group the total population doubling level (PDL) was determined. In emphysema, mean+/-sem DT was 33.6+/-2.8 h compared with 24.8+/-1.4 h in controls. The differences in DT were preserved after cryopreservation. Groups also differed in the initial slope of the PDL plot during long-term culture (up to 35 days). However, the median (range) maximum PDL did not differ significantly between groups (13.8 (7.4-22.6) versus 20.2 (11.2-25.5)). The current authors, therefore, suggest that the reduced proliferation rate in vitro of lung fibroblasts from patients with emphysema reflects a persistent, intrinsic failure of cellular replacement and maintenance in this disease, possibly in relation to pre-term aging.