A retrospective evaluation of asymptomatic subjects with persistent elevation of serum creatine kinase (CK) levels (hyperCKemia) was made in order to verify the presence of subclinical myopathy or idiopathic hyperCKemia and to define the most appropriate diagnostic pathway. Persistently increased serum CK levels are occasionally encountered in healthy individuals. In 1980 Rowland coined for them the term idiopathic hyperCKemia. Despite the increase of scientific knowledge, several healthy subjects with hyperCKemia still represent a problem for the clinician. We made a retrospective evaluation of 114 asymptomatic or minimally symptomatic individuals with incidentally detected persistent hyperCKemia. They underwent neurological examination and laboratory/instrumental evaluation. Skeletal muscle biopsy was performed and thoroughly investigated. Biochemical and genetic investigations were added in selected cases. Logistic regression analysis was applied. We diagnosed a neuromuscular disorder in 21 patients (18.4%), and found, by muscle biopsy and/or EMG, pathological but not conclusive findings in 57 subjects (50%). The statistic correlation between elevated serum CK levels and the probability of making a diagnosis changed according to the age of the patient. Conclusions Muscle biopsy is the basic tool for screening asymptomatic subjects with hyperCkemia. It allowed us to make a diagnosis of disease in 18.4% of patients, and to detect skeletal muscle abnormalities in 38.6% of the subjects. Interestingly, 31.6% of individuals had completely normal muscle findings. These best fit the "diagnosis" of idiopathic hyperCKemia.