The present discussion of SMI is of major impact on physical active coronary patients, since SMI during physical training could represent a potential risk factor. We carried out an investigation in 107 coronary patients of ambulant coronary groups (ACG) on the incidence of SMI during exercise testing and Holter monitoring (HM) including a training unit. With both techniques in approximately 1/3 of the patients SMI could be observed, when coronary medication was omitted. However the concordance of these two positive groups was found to be remarkably low. During HM SMI was found within the training units nearly as frequent as during normal daily life. By beta blockade (100 mg metoprolol) exercise SMI during HM was suppressed in 2/3. Our conclusion was that SMI is not of major significance in pharmacologically well controlled participants in ACG.