The deoxyribonucleic acid patterns in lymph node metastases in relation to the degree of ploidy and proliferation in the primary bladder tumor were evaluated in 162 patients who underwent cystectomy for muscle invasive bladder carcinoma. The 34 diploid tumors had given rise to lymph node metastases in only 2 cases (6%), whereas 34% of the aneuploid tumors had metastasized. The frequency of lymph node metastases increased with the proportions of S-phase cells. In transitional cell carcinoma all tumors with a proportion of S-phase cells exceeding 20% had metastasized, while tumors with a proportion of S-phase cells between 10 and 20%, and less than 10% had metastases in 50 and 33%, respectively. The degree of ploidy of aneuploid tumors seems to be of importance for the potential to give rise to metastases, since the majority of metastatic tumors were in the triploid-tetraploid and hyperdiploid but not hypertetraploid regions. The degree of ploidy of lymph node metastases was in good agreement with that of the primary tumors.