Counting of cells in cerebrospinal fluid is currently performed manually. Because of the inherent analytical and economical disadvantages, we attempted to introduce a fully automated method. Therefore, we validated the Abbott CellDyn-4000 haematology analyser for counting cells in cerebrospinal fluid. The analyser was used in its standard configuration with the simple precaution of a preceding blank sample. As for leukocyte counting the analyser yielded high precision (CV approximately 5% above the upper reference limit), good linearity, low limit of detection (2/microl) and excellent correlation (r > 0.99) with the counting chamber method. The differential leukocyte count was equally accurate and precise, even in the low concentration range. Performance of the erythrocyte count was impaired by its high limit of detection (6/nl) and it appeared satisfactory only for detecting blood admixture due to traumatic puncture. The specificity of the analyser is excellent, since it correctly classified non-viable leukocytes and excluded yeast cells from the leukocyte count in a patient with cryptococcal meningitis. We conclude that the CellDyn-4000 is well suited for quickly and reliably counting leukocytes in cerebrospinal fluid. Developing some software modifications might make the analyser useful also for performing erythrocyte counting in cerebrospinal fluid.