The historical evolution of the spherical roller bearings is discussed briefly. The difrent internal and external designs common in today's market are evaluated regarding their load carrying ability, roller guidance, and friction. It can be shown that all these criteria have to be evaluated simultaneously with a view towards the application conditions expressed by the load magnitude, load angle, load direction changes, speed, speed changes and mounting conditions. It can also be shown that the method of guiding the rollers by means of a retainer or by means of an integral center flange are equally valid and equally efficient methods under most application conditions. In cases of extreme application conditions, however, it is evident that the positive guidance of the rolling elements through an integral centerflange will result in lower friction, i.e. better running conditions. It is also shown that other design factors besides the retainer and center flange are available such as the splitting of the bearing rings in axial and circumferential direction, to modify a bearing for special application conditions.