Bile duct brushings (BDB) are the method of choice for pathological diagnosis of malignancy of the hepatobiliary system in our institution. We examined results of the cytological assessment of 267 BDB and compared them with biopsies, which were available in 131 cases. Sensitivity of BDB for diagnosis of malignancy was 44% and specificity 100%, in keeping with the experience of others. The review of "false-negative cases" reveals four main reasons for the relatively modest sensitivity of BDB in diagnosis of malignancy: poor sampling, lack of diagnostic criteria for dysplasia-carcinoma in situ, difficulties in recognition of special tumor types, and underestimating the significance of the smear background. After a critical review and with regard to these issues, the sensitivity of BDB in our series could have been improved to 78%. We conclude that BDB can give a confident and definitive diagnosis of malignancy, which can be relied upon without a tissue biopsy. A negative result does not exclude malignancy.