We analysed the sample of gypsies included in the Spanish Collaborative Study of Congenital Malformations (ECEMC), a hospital based, case-control study and surveillance system. Special emphasis was placed on the birth prevalence of recessive multiple congenital anomaly syndromes, comparing their frequency in the gypsy population with that observed among non-gypsies. We observed an increased prevalence of birth defects, mostly because of groups of children with patterns of multiple anomalies and with autosomal recessive syndromes. The latter were approximately seven times more frequent in gypsies than in non-gypsies. We also estimated the carrier frequency in both groups (gypsy and non-gypsy). We consider that the frequent occurrence of the conditions observed reflects the high rate of consanguineous couples among the Spanish gypsy population.