A sensitive, safe and cheap method to detect minimal residual disease (MRD) is here presented. The PCR-GS technique includes: (a) a fluorescent PCR for the IgH region with CDR3/JH consensus primers; (b) the electrophoresis on an automatic sequencer (ABI PRISM 310); (c) the analysis of results by the GeneScan program. A total of 72 samples were analysed: 34/49 B-cell Non-Hodgkin's Lymphoma (NHL) (69%), six out of seven Multiple Myeloma (MM) (86%), 1/2 Hodgkin's Disease (HD) and 4/4 Acute Lymphoblastic Leukaemia (ALL) were found to be positive, showing a monoclonal IgH rearrangement. The major bias of the PCR-GS method are the 21% of false negatives, but 13/15 negative patients carried t(14;18); consequently, the association of the evaluation by PCR assays of the IgH and BCL2/JH rearrangement allowed to detect a molecular marker of B-neoplasia in more than 94% of tested samples.