Short tandem repeats or STRs on the non-pseudoautosomal region of the Y-chromosome are polymorphic markers used to obtain a specific male DNA profile to unravel special cases in the Legal Medicine casework. Haplotypes of Y-chromosome are constructed by analysis of many STRs. They allow solving paternity cases where the alleged father is not available, as well as forensic situations, as rape cases, where mixtures of male/female DNA are present. Five Y-linked STRs recently informed: A4, A7.1, A7.2, A10 y C4 (White et al. 1999) were PCR-typed in 101 mexican mestizos from the Northwest of Mexico by means of native polyacrilamide gel electrophoresis and silver staining. Allelic frequencies were estimated for each STR. Their gene diversity ranged from 57.1% for A-4 to 74.7% for C-4. Excepting for A-4, Mexican Y-chromosome STR allele distributions displayed similarity (p > 0.05) to the previously informed population. Seventy-five different haplotypes were observed from 98 complete haplotypes obtained. The haplotype diversity and the male discriminatory capacity of this five-locus system were 99.0% and 77.5%, respectively. This knowledge permits to use effectively these five Y-chromosome markers in legal medicine casework in the studied population. This STR-system is a new resource of Y-chromosome polymorphism that offers a great potential to identify males and male-lineages, and can be used confidentially in paternity testing and forensic analysis in Mexican population.