A malformed male newborn was first diagnosed as having Smith-Lemli-Opitz syndrome. Extensive cytogenetic studies, including Q, G, C, R and T banding and BudR treatment, were applied, finally leading the authors to conclude that the patient had a partial 2p trisomy caused by direct duplication 2p14 to 2p23. This was a de novo chromosome abnormality, as both parents had normal karyotypes.