Panels of immunological markers are useful in refining diagnosis in view of certain variability between B-cell leukaemias. A statistical multivariate approach was used on 100 B leukaemias (preliminary sample) to explore the potential value of the combination of CD43, and the classical markers CD5, CD23, CD79b, FMC7, CD22 and surface immunoglobulin to differentiate chronic lymphoid leukaemia (CLL) from lymphoma (non-CLL). CD43 was highly effective (P < 0.00001) and its inclusion in the panels improved the accuracy of discrimination in a 'control' sample of 74 B leukaemias to 98.6%. Inclusion of CD43 facilitates the diagnosis of B-lymphoproliferative disorders and improves their classification.