Two children with a partial monosomy 6q are reported: a girl with an interstitial deletion [46,XX,del(6)(q16.2q23.1)], and a boy with a terminal deletion [46,XY,del(6)(q25.1)]. Both children presented with developmental delay, facial dysmorphism and a cardiac defect. The patients have been studied using G banding and cosmid probes specific for the long arm of chromosome 6. Clinical data are compared with patients reported in the literature.