Background Deficiency of the sarcolemmal protein dystrophin has been linked to dilated cardiomyopathy. Some children with congenital muscular dystrophy have a deficiency of the laminin ⍺₂ chain of merosin, an extracellular matrix protein linked to dystrophin through a group of glycoproteins. It has been shown that deficiency in one of these glycoproteins is responsible for muscular dystrophy and dilated cardiomyopathy. Children with laminin ⍺₂ deficiency may be at risk for development of cardiomyopathy. Methods and Results We studied the cardiac function of a cohort of 16 children with congenital muscular dystrophy by using 2-dimensional echocardiography. The expression of the laminin ⍺₂ of merosin in the patients was determined on a skin or muscle biopsy. Two of 6 merosin-deficient children had an ejection fraction <40%. The average ejection fraction of the merosin-deficient children was 43% ± 11%, which was significantly lower than the merosin-positive children (53% ± 5%, P = .03). Conclusions This study suggests that a deficiency of laminin ⍺₂ can give rise to dilated cardiomyopathy, supporting the idea that defects of dystrophin, or of associated proteins, can cause dilated cardiomyopathy in addition to muscular dystrophy. (Am Heart J 1998;136:474-6.)