Abstract
A new method for obtaining the relativistic internal center-of-mass variables without using the singular Gartenhaus-Schwartz transformation is proposed. We have shown that the relativistic c.m. dynamical variables can be obtained from the nonrelativistic ones by a unitary transformation. A general method for determining the relativistic interaction in terms of a given nonrelativistic phenomenological potential is developed. Many different results obtained previously by various approaches have been reproduced.