In a prospective study the size of 157 pelvic tumors in 101 patients was measured preoperatively by bimanual palpation and vaginosonography, and the results were compared with measurements made at operation. In 72 uterine and 85 ovarian lesions the Spearman correlation coefficients (rs) between the three maximum diameters at right angles to each other measured at operation and by bimanual palpation ranged from 0.48 to 0.78. The correlation coefficients (rs) between measurements at operation and preoperative vaginosonography ranged from 0.91 to 0.97. The size of small lesions was overestimated by bimanual palpation; 44% of tumors smaller than 5 cm in diameter were only detected by vaginosonography.