Objective: To characterize the immunophenotypic features of CLL/SLL among patients diagnosed at Aga Khan University Hospital, Nairobi. Background: Cancer is a growing health burden worldwide. Rising to this challenge will require improved diagnostic services. Chronic lymphocytic leukaemia is common in elderly patients. Early laboratory criteria for diagnosis only required demonstration of persistent lymphocytosis and morphological evaluation. The current international standard in diagnosis however, incorporates findings of immunophenotyping. Facilities for immunophenotyping have generally been unavailable in Kenya. The Royal Marsden Hospital criteria (RMH) provide a scoring system that enables CLL/SLL to be distinguished from other mature B cell disorders. Method: A laboratory based cross sectional survey conducted from August 2011 to April 2012. A census of eligible cases was conducted. Potential cases were identified based on the French-American-British (FAB) morphologic criteria for CLL. Consecutive samples were obtained and subjected to 3 colour immunophenotyping on a Beckman Coulter Cytomics FC 500 cytometer. A limited panel of antibodies was used. These included CD5, CD19, CD22, CD23, FMC7, kappa and lambda. CLL/SLL was defined using the RMH scoring system. The baseline clinical and diagnostic data were also obtained. Results: Forty nine cases met the eligibility criteria. Thirty one were known CLL cases and 18 were newly diagnosed. Median age at diagnosis was 62 years (range 45-95 years). Male: Female ratio was 1.3:1. Black patients were more likely to present with high risk disease (Rai stages III-IV) and with higher lymphocyte counts than non-blacks at diagnosis. 26.5% presented in Rai stage 0. The prevalence of CD5/CD23 co-expression in cases defined as CLL was found to be 95.9%. CD5 was universally expressed whereas CD23 was present in all but 2 cases. Both were associated with atypical morphology. Complete absence of light chain expression using a monoclonal antibody was found in 12.2% of cases. Five patients had their diagnosis revised. Of 30 patients on follow-up for CLL, only 1 in 6 had had any form of immunophenotyping done. Conclusion: Immunophenotyping is diagnostically productive and should be part of the diagnostic workup when a chronic lymphoproliferative disorder is suspected.