To the Editor.— Recently, Porter et al (1981;245:1545) reported two cases of rhabdomyolysis in patients withStreptococcusand picornavirus infection. The observations of the authors are of importance because they add these infectious agents to the already long list of viruses and bacteria involved in the pathogenesis of atraumatic rhabdomyolysis and myoglobinuric renal failure. However, we have some objections concerning the serum myoglobin measurement mentioned by the authors in case 1. They state that despite extremely elevated serum creatine phosphokinase levels (114,000 IU/L), "the serum myoglobin assay findings were normal." According to our experience with 23 cases of atraumatic rhabdomyolysis, this seems to be impossible: muscle damage causing enzyme leakage invariably leads to concomitant increases in serum myoglobin concentrations. Even in cases with minor degrees of rhabdomyolysis (as judged from serum creatine phosphokinase levels), serum myoglobin is regularly and notably elevated.1,2In the presence of renal failure, as in