Good motor performance depends on the electrical and mechanical design, as well as on motor operating conditions. Sound mechanical design reduces the vibration levels and extends the life of the machine. Over the years, the demand continues to grow for motors with greater reliability. When done properly, a high degree of reliability can be achieved while keeping economics in mind. This article discusses induction motor vibration, how the American Petroleum Institute (API) 541 views it, and what it means to the customer and manufacturer. It also discusses the evolution of the standards commonly used today and how the various requirements attack different vibration concerns. Any reference to API vibration in this article refers to API 541 fourth edition, unless otherwise stated.