The relationship between the quantity of silver-binding nucleolar organizer regions (AgNORs), nuclear DNA content, and proliferative activity was studied in 61 patients with adenocarcinoma of the lung. The proliferative activity of adenocarcinoma was estimated by tumor volume doubling time based on chest X-ray findings. There was a high, inverse correlation between the AgNORs and the tumor doubling time (p less than 0.001, r = -0.815), and the contribution rate was high value (2 = 0.664). However, the AgNORs value was an independent prognostic factor for survival time. A better 5-year survival rate was observed in patients with DNA diploidy than in DNA aneuploidy, but there was no statistical difference between the two groups. There was an inverse correlation between the DNA index and tumor doubling time (p less than 0.05, r = -0.565), but the contribution rate had a low value (r2 = 0.319). These results indicate that the AgNORs value is important in providing an estimate of the proliferative activity of adenocarcinoma.