Tumour cells from 74 biopsies from human urinary bladder carcinomas were cultivated in a semisolid system (Courtenay and Mills method). In 51 cases DNA flow cytometry (FCM) was performed. Significant growth was obtained in 53 of 74 cases (71.6%), and good quality DNA histograms from FCM were obtained in all 51 attempts. No correlations between clinical or histopathological data and plating efficiency (PE) were found, nor between ploidy and PE. However, a very high S-phase (greater than 15%) correlated with a low PE. This work shows that bladder carcinoma cells can be studied in a semisolid agar system. It also suggests that there exists no correlation between PE and DNA FCM data or clinical or histopathological data.