Macroscopic and microscopic features of tumours have been analysed in 37 bronchiolo-alveolar carcinomas. Lymphocytes, Langerhans cells, collagen (mature and/or myofibroblastic), were quantitatively or semiquantitatively evaluated. Histology, stage, type of fibrosis, nuclear profile features (area and shape factors), amount and type of mucin secreted, number of mitoses, Langerhans cells, myofibroblasts and LeuM1+ cells were not related to survival. Gross morphology of the tumour and, to a lesser extent, lymphoid infiltrates (in particular UCHL1+ and L26+ peritumoral lymphoid cells) were the only variables significantly related to survival. Estimated survival functions were computed according to Cox's model: well demarcated tumours behaved significantly better than poorly demarcated tumours and even more so than diffuse or multiple mass. Lymphoid infiltrates were significantly more represented in and around well demarcated tumours: however, their survival predicting value was less than that of the gross type.