During a 4-years period 122 patients admitted to the cardiologic hospital in Lille presented a significative positivity of serological reaction against Coxsackievirus B. Among these patients 19 suffered from acute pericarditis, 4 from cardiac arrhythmias, 3 from Bornholm syndrome and 14 from apparently primary congestive cardiomyopathy. In most of these 14 patients representing 18.4% of congestive cardiomyopathies investigated at the same time, hemodynamic studies and heart scanning with radioactive gallium were performed. 7 of these patients had a chronic (group A) and 7 an acute evolution (group B). In group A the scans were negative 4 times out of 5, whereas in group B they were positive in 5 out of 5 examinations. The control group including 3247 patients coming from the Institut Pasteur exhibited serological positivity in 4.6% of cases. Comparison of this group with that of cardiomyopathies shows a significant difference (p less than 0.001). The authors draw the attention to the frequency of positive serodiagnosis in congestive cardiomyopathy and stress the importance of gallium scintiscanning.