Relations Between Internal Symmetry and Relativistic Invariance

The problem of combining relativistic invariance and internal symmetry is reviewed, and a critical evaluation of very recent papers on this subject is made. It is proposed that the Poincaré group $P$ is not a subgroup of the group $E$ of invariance of a relativistic quantum theory, but is the quotient $P=\frac{E}{S}$, where $S$ is the internal symmetry group. Pertinent mathematical results are given.