Stereotactic core biopsy (CB) using 14-gauge needles was adopted as the standard method of diagnosis of screen-detected breast microcalcifications (MC) at Sir Charles Gairdner Hospital in 1996. Fine needle aspiration (SFNA) was included as an adjunct, to optimise sensitivity and to provide immediate reporting. Recently, core imprint cytology (CI) has been shown to have a high sensitivity in diagnosing malignancy. The aims of this paper were to evaluate the accuracy of SFNA as an adjunct to CB, and whether CI could replace SFNA for immediate reporting in MC. Part A is a retrospective review of CB/SFNA of screen-detected MC from May 1998 to February 2000. A minimum of five cores was performed. SFNA samples were restricted to a maximum of three needle passes. Part B is a prospective study of CI from May to November 2000. In Part A, there were 406 MC in 353 women and 81 carcinomas were proven on excision. The complete sensitivity of CB for a diagnosis of malignancy was 97.5% and of SFNA was 65%. No false-positive diagnoses were made by either method. No extra carcinomas were detected using SFNA. In Part B, CB/CI were performed on 203 MC from 165 women. There were 38 carcinomas and 30 of these (79%) were diagnosed as malignant on CI. No false-positive diagnoses were made. The predictive value of a benign diagnosis was 95%. SFNA had little value as an adjunct to core biopsy in MC. CI promises to be useful in providing same day diagnosis for counselling purposes and for planning future surgery.