From January 1954 to December 1985 cardiac myxoma was diagnosed in 75 patients at the Mayo Clinic. The clinical presentation was typical in 70 cases and was referred to as "sporadic myxoma". Forty four other cases of cardiac myxomas (five from the Mayo Clinic) presented with a combination of distinctive clinical features and these cases are described as "syndrome myxoma". The patients with syndrome myxoma were younger (mean age, 25 vs 56 years) and had unusual skin freckling (68%), associated benign non-cardiac myxomatous tumours (57%), endocrine neoplasms (30%), and a high frequency of familial cardiac myxoma (25%) and familial endocrine tumours (14%). The two types of cardiac tumour were different (syndrome vs sporadic): atrial location, 87% vs 100%; ventricular location, 13% vs 0%; single tumour, 50% vs 99%; multiple tumours, 50% vs 1%; and recurrent tumour, 18% vs 0%. It is concluded that patients with syndrome myxoma represent a distinctive subgroup in which there are important clinical, surgical, and genetic implications. More importantly, syndrome myxoma appears to be only one expression of a much larger disease entity.