The preoperative results of sonography of 108 malignant breast tumors were analysed for reasons of false negative results by correlation of sonographic features with the corresponding clinical, histological and cytological findings. Previously we found no typical sonographic criteria of malignancy. Here we show, that diagnosis was especially difficult in carcinoma of young women, and in estrogen receptor negative, as well in progesterone positive tumors. The accuracy of diagnosis of tubular carcinoma was lower than of solid carcinomas. There was no correlation between false negative ultrasound results an histological or cytological grading, nuclear size, or tumor mitosis rate. We emphasize the importancy of sonography in diagnosis of female breast cancer.