Objectives. Estimate the effect of atorvastatin on muscular symptom intensity in coronary patients with subjective statin-associated muscle symptoms (SAMS) and to determine the association with blood levels of atorvastatin and its metabolites, to obtain an objective marker for true SAMS. Design. A randomized, double-blinded, cross-over study will include 80 coronary patients with subjectively reported SAMS during ongoing atorvastatin therapy or previous muscle symptoms that led to discontinuation of atorvastatin. Patients will be randomized to 7-weeks treatment with atorvastatin 40mg/day in the first period and matched placebo in the second 7-weeks period, or placebo in the first period and atorvastatin in the second period. Each period is preceded by 1-week wash-out. A control group (n=40) without muscle symptoms will have 7 weeks open treatment with atorvastatin 40mg/day. Blood samples will be collected at baseline and at the end of each treatment period, and muscular symptoms will be rated by the patients weekly using a Visual Analogue Scale (VAS). The primary outcome is the difference in aggregated mean VAS scores between the last three weeks of atorvastatin treatment and of placebo treatment. The main purpose is to develop an objective marker for true SAMS, by comparing SAMS associated with blinded atorvastatin treatment with blood concentrations of atorvastatin and its metabolites. Diagnostic and discrimination performance will be determined. Conclusions. The study provides new knowledge on SAMS in coronary patients and may contribute to more personalized statin treatment and monitoring, fewer side-effects and consequently improved adherence and lipid management in future practice.