Human myelin basic protein (hMBP) gene is one of the candidate genes in the complex mosaic of multiple sclerosis (MS) susceptibility. In this study we verified the distribution of the polymorphism of the region 5' flanking the first exon of the hMBP gene, in 97 relapsing remitting, 74 primary progressive Italian MS patients, and in 236 healthy controls, using polymerase chain reaction (PCR) and gel electrophoresis analysis in this region from 1116 - 1540 nt. Three different band patterns were observed: one homozygote with a 354 bp long fragment, one homozygote with 424 bp long fragment and one heterozygote with both bands present. The short fragment was statistically more frequent in RRMS patients than in HC (P<0.05). The long fragment was more present in HC. Similarly the short homozygous pattern (354 bp/354 bp) was significantly higher in the RRMS patients versus the healthy controls (P<0.01). The sequence analysis of the hMBP alleles showed that while the long fragments matched the prototype sequence completely, all the short fragments showed a deletion of 70 bp from nt 1177 to nt 1247, which explains the short 354 bp allele detected by PCR. Moreover two single mismatches in positions 1386 (T-->C) and 1431 (G-->A), were present only in the short hMBP fragment.