359 patients with non-Hodgkin lymphomas referred to Oulu University Hospital between 1964 to 1981, inclusive, were reclassified histologically according to the criteria of Lukes-Collins as well as Lennert's histological classifications. The requirements to enter this study were fulfilled only in 280 cases. After the evaluation of the results certain observations emerged. Firstly, within the Lukes-Collins classification: Nodularity was predominantly related to the SC and LC types. Nodularity is indicative of better survival. The Lukes-Collins classification correlates well with clinical stage as well as with age. The Burkitt and convoluted types were found to be predominantly related to childhood or to younger patients and the non-Burkitt type most frequently to the older groups. The Lukes-Collins classification separates well two clear prognostic groups, the favourable group (LC, SC, PC, and SL types), with an overall median survival of 44 months, and the unfavourable group (LNC, IS, convoluted, undefined, and SNC types), with an overall median survival of 11 months. No differences in survival were observed between the LNC, LC, and IS diffuse types. Stage, general symptoms and laboratory findings were also evaluated. Secondly, within the Kiel classification: Nodularity has been found mainly in the CB-CC type, but also in 27% of the CC cases. The relationship of the subtypes according to the Kiel classification and age resembles the same relation found with the Lukes-Collins classification. According to the Kiel classification, the Burkitt, convoluted, and lymphoblastic types were related to children and young adults. A proportion of the LB type occurs also in older groups. Three prognostic groups were identified, the favourable (CB-CC foll. and PC types), with an overall median survival in excess of 80 months, an intermediate group (CB-CC foll. - diff., CC, and CLL), with an overall median survival of 38 months, and an unfavourable group (Conv, CB, CB-CC diff., UC, IB, and Burkitt types), with a median survival of 11 months. The CC type in this study was controversial in its morphological acceptability.