We describe the case of a 22-month-old boy with developmental and psychomotor retardation as well as craniofacial dysmorphism, including a cleft lip. Analysis of G-banded chromosomes of the propositus showed a de novo interstitial deletion of the short arm of chromosome 3, del(3)(p13p11). Fine mapping of the deletion was performed using fluorescence in situ hybridisation analysis with region-specific BAC clones. Eight BACs were absent from one chromosome 3 from the patient. Molecular analyses of eleven polymorphic DNA markers helped to narrow down the breakpoints and demonstrated that the derivative chromosome 3 is of paternal origin. The deleted segment encompasses about 15 Mb between marker D3S3551 and the centromere. Only a small number of known genes, including PROK2, GPR27, RYBP, PPP4R2, ROBO1, and GBE1, which map in the 3p13-p11 region are included in the deletion.