We report here a de novo 16q24.1 interstitial duplication in a woman with a severe phenotype consistent with mental retardation, spastic paraplegia, severe epilepsy, a narrow and arched palate, malar hypoplasia, little subcutaneous fat and arachnodactyly. Although conventional karyotyping was found to be normal, array-CGH detected a small duplication on chromosome 16. Using QFM-PCR, we characterised its proximal and distal breakpoints. The duplication, which is approximately 250 kb, encompasses seven genes (KIAA0182, GINS2, c16orf74, COX4NB, COX4I1, MIR1910 and IRF8). Several reports have previously described large 16q duplications, and some of these overlap with our region in 16q24.1. Due to the variability of the described phenotypes, the characterisation of small 16q duplications may help to determine critical regions and the genes they contain that are associated with the components of complex phenotypes.