We have evaluated 16 Y-chromosomal microsatellites for forensic purposes. The loci were amplified in two multiplex PCRs, a 9-plex (http://www.ystr.charite.de./ index_gr.html) and a 10-plex (Ch.M. Rutberg and J.M. Butler, pers. comm.), with three common Y microsatellite loci. Of these 16 loci 9 belong to the widely used Ychromosomal minimal haplotype (DYS19, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS385a and DYS385b), and the additional 7 loci were DYS435, DYS436, DYS437, DYS438, DYS439, Y GATA A7.1 and Y GATA H4. The PCR products were subsequently analysed using capillary electrophoresis. For population studies and PCR validation purposes, DNA samples from 200 Finnish males, 20 female samples and various male animal samples were analysed with both multiplex PCRs. To compare the sensitivity of the 9-plex and the 10-plex reactions, we performed the multiplex PCRs with samples from a dilution series of a known amount of DNA. Our results show that the 9-plex PCR is more sensitive than the 10-plex PCR. In addition, the 10-plex PCR showed constant, unspecific peaks which were detected in male and in female samples. When using the set of minimal haplotype markers, our 200 Finnish male DNA samples fell into 85 different haplotypes, 64 (75%) of them occurring only once in our data. When we were using data from 10-plex, we found 72 different haplotypes, 52 (72%) occurring only once. Combining the data, together 120 different haplotypes were found, and from these 99 (82.5%) occurred once. In the 9-plex PCR, 26.5% of the Finns had the most common haplotype. Similarly in the 10-plex PCR also 26.5% of Finns shared the most common haplotype. However, when the two marker sets were combined, the most common haplotype was shared only in 13% of the samples. The power of discrimination values of separate microsatellite loci varied in the 9-plex PCR between 0.448 (DYS392) and 0.706 (DYS385a and b together) and in the additional seven loci between 0.020 (DYS436) and 0.523 (Y GATA H4).