AIMS: To compare the ability of four commonly used PCR techniques to demonstrate clonal IgH rearrangements in multiple myeloma. METHODS: Bone marrow samples (containing a minimum of 10% plasma cells) were obtained from 127 patients with confirmed multiple myeloma. Framework 3 (Fr3) PCR was performed in all cases and the Framework 1 (Fr1f) PCR, which utilises six VH family specific primers, in 98 cases. In addition, 44 cases were assessed by Fr3, Fr1f, Framework 2 (Fr2) and Framework 1 consensus (Fr1 con) PCR techniques. JH primer selection was also assessed such that each PCR strategy was performed twice in each of the 44 cases, using the JH consensus primer (JH con) alone and then repeated with an equimolar mixture of JH con, JH3 and JH6 (JH mix). RESULTS: Clonal rearrangements were demonstrated in 71 (56%) of 127 cases with the Fr3 PCR and in 52 (53%) of 98 with the Fr1f PCR. However, by using both techniques it was possible to demonstrate clonal IgH rearrangements in 92 (75%) of 122 cases. Forty four cases were assessed by all four PCR techniques; in these cases the Fr3 and Fr1f PCRs demonstrated clonal rearrangements in 26 (59%) cases with a combined yield of 34 (77%). The Fr2 and Fr1 con PCR techniques had inferior pick up rates, demonstrating clonal rearrangements in 21 (48%) of 44 cases and a combined yield of 28 (63%). The Fr2 PCR did, however, demonstrate a clonal rearrangement in one case negative by both Fr3 and Fr1f. Two additional rearrangements were demonstrated by using JH mix; one became positive by Fr3, Fr1f and Fr2 and the other positive by Fr1f, Fr1 con and Fr2. CONCLUSIONS: By utilising both the Fr3 and Fr1f PCR techniques it is possible to demonstrate definitive clonal rearrangements in the majority of patients with multiple myeloma. The Fr1 con and Fr2 PCR techniques have inferior pick up rates but may detect some additional rearrangements.