We report on the second case of duplication (4)(q12q13) with microcephaly, mental retardation, and minor facial anomalies. Duplications involving the distal region of chromosome 4q are well described and share common clinical findings. However, phenotypic abnormalities of duplications of the proximal portion of chromosome 4q are relatively unknown. A comparison of the clinical manifestations of our patient and the single published case suggests that the phenotype of this proximal 4q duplication is relatively mild. This study emphasizes the need to perform chromosome analysis in similar mildly affected/nonspecific cases.