Background: The polymerase chain reaction (PCR) has become a useful method to determine monoclonality in T-cell lymphomas. The authors investigated a number of T-cell lymphoma cases to determine (1) the monoclonality detection rate in South African T-cell lymphoma cases and (2) whether variation in detection of monoclonality exists in T-cell lymphoma subtypes. Methods and Results: Thirty T-cell lymphoma cases, including pleomorphic peripheral T-cell lymphomas, precursor T-lymphoblastic lymphomas, large-cell anaplastic lymphomas, and one cutaneous lymphoma, were assessed. DNA was purified from paraffin-embedded tissue and amplified with consensus oligonucleotide primers directed at the rearranged T-cell receptor-gamma genes. Monoclonality was found in 73% of cases, similar to previous reports. Pleomorphic peripheral T-cell lymphomas (89%) were detected most successfully; lymphoblastic (73%) and large-cell anaplastic lymphomas (58%) had lower detection efficiencies. Conclusions: Some T-cell lymphoma subtypes are less successfully detected; additional primer sets should be used to improve detection.