The study presents preliminary qualitative findings of an investigation of grossly normal main and lobar bronchi at sites distant to well circumscribed tumour (n = 15), adjacent to tumour (n = 5) or of airways obtained during heart/lung transplantation in patients with cystic fibrosis (CF, n = 3). In the normal airways the surface epithelium was on average 50 micron thick, pseudo-stratified and rested on a roughly contoured basement membrane. A variety of cell types were identified although many were obscured by a dense covering of cilia, occasionally interrupted by foci of squamous metaplasia. Submucosal gland structure was observed in chance vertical fractures of the airway wall. Tissue adjacent to tumour showed sloughing, squamous metaplasia, pleomorphism and cell surface projections of stubby microvilli or tortuous microridges. The surface morphology of the three CF patients showed no feature unique to the condition, albeit secretions were found adherent to surface lining associated with isolated bacteria and groups of free cells (probably lymphocytes). In each of the three cases the epithelial surface was densely ciliated, interspersed with mucous (i.e., goblet) cells. Submucosal gland collecting ducts had dilated lumena.