Dear r-help, I want to solve an equation XR=B where R is a regular 10x10 upper triangular matrix and B a 100x10 matrix. I do X=B%*%solve(R) which work well but I need to do this operation a great number of time and this is very long. With my pentium 2.4 GHz, Windows XP and R 1.7.0, I do this 100000 times in 58 seconds (for comparaison Scilab take 22 seconds and Matlab only 8 seconds to do the same thing). So, I try backsolve with X=t(backsolve(R,t(B),transpose=TRUE)) or X=t(backsolve(t(R),t(B))) but this is longer (more than 1 minute 10). Is there a mean to to this more rapidly with R ? Thank you very much P. Grandeau ---