The related immunomodulatory neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylyl cyclase activating peptide (PACAP; gene symbol ADCYAP1) have recently been proposed as novel therapeutics for the treatment of multiple sclerosis (MS). These neuropeptides, as well as those belonging to the tachykinin family exert pleiotropic effects, many of which are of relevance to central nervous system inflammation. In the present study, we have analysed 14 single nucleotide polymorphisms (SNPs) and 4 microsatellite markers in the VIP, ADCYAP1, TAC3 and TAC4 genes for susceptibility to MS in a case-control collection from Northern Ireland. Following correction for multiple comparisons, we did not find any significant associations between single polymorphic markers or multiple-marker haplotypes and susceptibility to MS. Furthermore, we analysed 2 SNPs in the TAC1 gene in a set of Sardinian trio MS families, based on our previous observation of association of these SNPs with MS in the Northern Irish (Genes Immun. 2005, 6, 265-270). Analysis of these SNPs in the Sardinians was not significant though a similar trend to that originally observed in the Northern Irish was present. Meta-analysis of the Sardinian and Northern Irish TAC1 SNP genotype data revealed a Mantel-Haenszel Common OR Estimate for the TAC1 intron 1 SNP rs2072100 of 0.76 (95% CI 0.63-0.92; P=0.005; A allele) and for the TAC1 promoter SNP rs7793277 of 0.76 (95% CI 0.615-0.95; P=0.014; C allele). Our data advocate a need for further exploration of the TAC1 gene region in MS.