Discrimination between allele peaks and stutter peaks is important in STR typing for forensic purposes. In minus stutter, it is known that there are correlations between alleles and stutter ratios, but there are few reports on other types of stutter such as plus stutter. In this study, we examined the relationship of alleles to stutter ratios in Y-STR typing using the Yfiler^TM Plus PCR Amplification Kit. DNA was extracted from blood samples collected from Japanese males and multiplex PCR amplification was performed with 1 ng DNA template. In minus stutter, high correlation coefficients ( r >0.7) between alleles and stutter ratios were observed in 23 of 25 markers. Meanwhile, in other types of stutter, only the forward stutter in DYS392 showed such a high correlation coefficient. These results can be used for interpretation of electropherogram data in forensic Y-STR typing.