OBJECTIVE: To compare the karyotype of babies conceived through ICSI with that of naturally conceived babies. DESIGN: Prospective controlled study. SETTING: The Egyptian IVF-ET Center, Cairo, Egypt. PATIENT(S): Four hundred and thirty babies conceived through ICSI and 430 babies conceived naturally. INTERVENTION(S): ICSI and karyotyping. MAIN OUTCOME MEASURE(S): Abnormal karyotype. RESULT(S): Four hundred and thirty consecutive babies conceived through ICSI who were delivered in one hospital had 15 abnormal karyotypes (3.5%). Of the 15 babies, 7 were of female phenotype and 8 of male phenotype. Six babies had sex chromosome anomalies, 8 had autosomal anomalies, and 1 had combined sex chromosome and autosomal anomalies. A control group of 430 consecutive babies conceived naturally who were delivered in one hospital had no abnormal karyotype. The difference between the two groups was significant (P