A case of 49, XXXYY chromosome anomaly in an adult male is reported. Features of Klinefelter's syndrome are predominant among the clinical findings. Characteristics suggestive of acromegaly have been associated with this chromosomal anomaly. Despite prognathism and an overhanging brow, acromegaly was not present in this case. Psychological traits sometimes reported in males with the XXY and XYY karyotypes were seen in this patient, but the variability of expression of these characteristics calls into question the validity of their correlation with the presence of supernumerary sex chromosomes.