Let R ∈ C n×n be a nontrivial involution; i.e., R = R −1 / = ±I . We say that A ∈ C n×n is R-symmetric (R-skew symmetric) if RAR = A (RAR = −A).There are positive integers r and s with r + s = n and matrices P ∈ C n×r and Q ∈ C n×s such that P * P = I r , Q * Q = I s , RP = P , and RQ = −Q. We give an explicit representation of an arbitrary R-symmetric matrix A in terms of P and Q, and show that solving Az = w and the eigenvalue problem for A reduce to the corresponding problems for matrices A P P ∈ C r×r and A QQ ∈ C s×s . We also express A −1 in terms of A −1 P P and A −1 QQ . Under the additional assumption that R * = R, we show that Moore-Penrose inversion and singular value decomposition of A reduce to the corresponding problems for A P P and A QQ . We give similar results for R-skew symmetric matrices. These results are known for the case where R = J = (δ i,n−j +1 ) n i,j =1 ; however, our proofs are simpler even in this case. We say that A ∈ C n×n is R-conjugate if RAR =Ā where R ∈ R n×n and R = R −1 / = ±I . In this case (A) is R-symmetric and (A) is R-skew symmetric, so our results provide explicit representations for R-conjugate matrices in terms of P and Q, which are now in R n×r and R n×s respectively. We show that solving Az = w, inverting A, and the eigenvalue problem for A reduce to the corresponding problems for a related matrix S ∈ R n×n . If R T = R this is also true for Moore-Penrose inversion and singular value decomposition of A.