The authors reviewed 316 cases of breast carcinoma diagnosed from January 1, 1986, to December 31, 1989. Clinical data and mammograms were available for all patients. Of the 316 carcinomas, 272 (86.1%) were invasive; 37 (13.6%) of these represented pure invasive lobular carcinoma (ILC). Twenty-five (68.5%) of the 37 patients with ILC and 161 (70.3%) of the 229 patients with invasive ductal carcinoma (IDC) presented with clinically palpable masses. Asymmetric opacities and architectural distortion were the predominant mammographic signs in 21 (57%) of the cases of ILC but only 32 (13.6%) of the cases of IDC. Malignant calcifications were not present in any of the patients with ILC but were present in 110 (47%) of those with IDC. Of the ILC lesions, 29 (85%) [corrected] had the same opacity as that of normal fibroglandular tissue, and the mammographic findings were often subtle and seen initially on one view only. There was no substantial difference in the TNM stage at diagnosis between the two study groups.