AbstractA kinetic bioluminescence assay with optimized reagent conditions has been developed for application as a screening test for increased creatine kinase (CK) activities in dried blood spots. This test is used for the early detection of Duchenne muscular dystrophy (DMD) in a voluntary CK screening program in West Germany of the 176,600 boys tested up to December 31, 1984, 48 who were less than 6 months old had certain or probable DMD (frequency 1: 3679). In 1983 and 1984, the rate of false positive results was 0.016% for a cut‐off activity 300 U/liter and 0.061% for a cut‐off activity 180 U/liter. Long‐term counseling is offered to families of newly detected DMD patients in order to facilitate the aims of the screening program, namely, avoidance of secondary cases in affected families, early professional care for the sick child, and the early opportunity to make the appropriate decisions for a life with an handicapped child. Two types of a benign hereditary blood anomaly were also detected by CK screening (CK‐BB inside erythrocytes or thromb