All cases of acute myocardial infarction (AMI) can be divided into outpatient-onset AMI and in-hospital-onset AMI depending on the place and circumstances of their development. In this review we consider the problem of in-hospital AMI. Special attention is paid to specific features of its clinical manifestations and the scale of the clinical problem. Possible causes of difficulties in the diagnosis and treatment of this condition are presented in comparison with those in patients with outpatient-onset AMI.