Eight DYS385 allele size discrepancies and six DYS448 null types were detected among 708 Korean men when results of three in-house multiplex short tandem repeat (STR) systems were compared. The systems included both ordinary and reduced size amplicons. Sequence analysis revealed deletion mutations at two sites upstream of the DYS385 core repeats and deletion of the entire DYS448 locus. At DYS385, allele size differences were one or two repeats and were dependent on the primer set used for polymerase chain reaction (PCR) amplification. Location of the primer target sequence in a flanking region of the STR, distal or proximal to the deletion, determined allele size. Two widely used commercial kits amplify DYS385 so as to include the mutable sites. Arrangement analysis of sequence tagged sites demonstrated that the deletion patterns at DYS448 (and DYS464) were associated with arrangements of the azoospermia factor c gene (AZFc). The DYS448 deletion appears relatively frequent in Asians.