We aimed at establishing the correlation between karyotype of anembryonic and embryonic first trimester pregnancies and serum levels of beta-hCG, 17beta-estradiol and progesterone. Chromosomal analyses were performed on products of conceptions lower than 12 weeks, using standard-banding protocols. Measurements of 17beta-estradiol and progesterone were carried out by immunoenzymatic assays and beta-hCG by radioimmunoanalysis (RIA). Chromosomal analyses among 11 spontaneous abortions revealed 6 (54,5%) to be normal and 5 (45,5%) abnormal; of these latter, 4 were anembryonic pregnancies (44,4% total frequency). Serum beta hCG and beta-estradiol average levels were lower in the anembryonic pregnancies but did not reveal significant differences with normal levels. Hormonal levels were correlated with karyotype results and it was found that average beta-hCG value was 3.8 times higher in cases with abnormal karyotype than in those in whom it was normal (p <0.05). Linear correlation analyses between hormonal measurements in anembryonic pregnancies were statistically significant (p <0.05). Correlations between beta-hCG and progesterone, beta-hCG and 17-beta estradiol, and the latter with progesterone, proved to be significant in the group with abnormal karyotype (p < 0.05). Anembryonic pregnancies present high frequency of chromosomal anomalies; such pregnancies with abnormal karyotype have a high serum level of beta-hCG; this condition increased the rate of abortion.