A 35-year-old man with infertility was referred for chromosomal analysis. In routine cytogenetic analysis, the patient was seen to have additional material of unknown origin on the terminal region of the short arm of chromosome 4. To determine the origin of the unknown material, we carried out high-resolution banding, comparative genomic hybridization (CGH), and FISH. CGH showed a gain of signal on the region of $4q32{ ightarrow}q35$. FISH using whole chromosome painting and subtelomeric region probes for chromosome 4 confirmed the aberrant chromosome as an intrachromosomal insertion duplication of $4q32{ ightarrow}q35$. Duplication often leads to some phenotypic abnormalities; however, our patient showed an almost normal phenotype except for congenital dysfunction in spermatogenesis.