Charcot-Marie-Tooth disease (CMT) and hereditary neuropathy with liability to pressure palsies (HNPP) are the most frequent inherited disorders of the peripheral nervous system. They are clinically and genetically heterogeneous. A submicroscopic tandem duplication of 1. 5 Mb in chromosome 17p11.2-12 comprising the PMP22 gene is found in 70.7% of autosomal dominant Charcot-Marie-Tooth type 1 (CMT1) patients. A reciprocal deletion is found in 87.6% of HNPP patients. The size of the typical CMT1A duplication is too small for classical cytogenetics and the whole region including the CMT1A-REP elements is sometimes too complex for a single DNA analysis method. We present results of a multiplex PCR of 8 microsatellite markers with multicolour fluorescence primer labelling followed by fragment analysis on an ABI 310 Prism analyzer to simplify the diagnostic procedure. Results for 24 patients can be obtained within 24 h. This method was applied on 92 DNA samples of unrelated patients carrying a typical CMT1A duplication previously confirmed by two colour fluorescence in situ hybridization (FISH, probe c132G8) and EcoRI/SacI Southern blotting (probe pLR7.8). Three alleles of three different sizes were clearly detected at least once in 88 of them (95.6%). Subsequently this analysis was applied on 312 Czech patients and revealed a CMT1A/HNPP rearrangement in 109 out of them.