© 2014 The Royal Australian and New Zealand College of Radiologists. Aim The study aims to ascertain the significance of ultrasonically occult but mammographically suspicious parenchymal abnormalities, detected at screening mammography. Method A retrospective analysis was made on BreastScreen Western Australia data from January 2004 to December 2009. The study group included cases with a mammographic parenchymal abnormality, a negative ultrasound scan and a biopsy under stereotactic guidance. A comparable group of ultrasonically visible carcinomas was used as the control to compare with breast carcinomas in the study sample. Results Study population consisted of 469 cases. Twenty per cent (n = 92) of the cases were breast carcinomas, with invasive ductal carcinoma (non-specified) being the most common histological type. There was a statistically significant increase in ductal carcinoma in situ and mucinous carcinoma within this malignant subgroup. Three per cent (n = 17) of the total cohort were borderline lesions on histology. The other 77% (n = 360) of cases were benign histology on core biopsy; however, one was subsequently diagnosed as an interval breast carcinoma. Conclusion Stereotactic-guided core biopsy of a suspicious mammographic parenchymal abnormality is warranted, regardless of a normal ultrasound scan, as up to 20% of these cases could be breast carcinomas.