Summary To identify the role of chromosome polymorphism in miscarriages, an analysis was carried out on 774 couples; 391 of them with two or more miscarriages and 383 serving as control. All couples were taken from two separate ethnic groups residing in the United Arab Emirates (UAE): 199 cases and 194 controls came from the indigenous population who are UAE nationals (Arabs) whilst 192 cases and 189 controls came from the Asian expatriate population residing in the UAE (Asians). Out of 391 cases, six Arab and three Asian couples were excluded because at least one partner had a chromosomal aberration. From the control group four Arab and four Asians were excluded for similar reasons. The remaining 757 couples were analysed to detect the presence of chromosomal heteromorphism in one or both partners. The results suggest that chromosomal heteromorphism was significantly increased in the Arab study population (P 0.05). Two heteromorphisms, 9qh and inversion (9)(p11q13) seem to be marginally related to recurrent miscarriages and only in the Arab study population. No differences were found in the distribution of chromosomal heteromorphism in couples analysed in relation to the number of miscarriages (two or more).