The prognostic value of quantitative histopathological parameters was evaluated in 55 consecutively treated patients with operable lung carcinoma of squamous and adenosquamous cell type. Using a projection microscope, estimates were obtained of mean nuclear volume (vV(nuc)), mean nuclear profile area, nuclear profile density, nuclear volume fraction, and mitotic profile frequency. Patient sex, age, and clinical stage was recorded. Single-factor analyses showed a prognostic significance of clinical stage and patient age (2p < or = 0.03), whereas sex was marginally significant (2p = 0.09). Of the quantitative histopathological parameters only estimates of vV(nuc) were of prognostic significance (2p = 0.02), in that small nuclear volumes were associated with the worst prognosis. In a multivariate Cox analysis, clinical stage, age, and vV(nuc) were found to be of significant, independent prognostic value. Thus, the present study indicates that vV(nuc) is of prognostic value, independent of clinical stage. The parameter is highly reproducible and easily obtained using unbiased stereology, and may be of future importance in the management of lung cancer patients.