Measurements are presented of the superconducting transition temperatures of concentrated alloys of aluminum containing Ti, V, Cr, Fe, and Co, prepared using an ultrarapid quenching technique. These results extend the concentration range of existing measurements by one or two orders of magnitude. We have analyzed our data using the theories of Kaiser and of Rivier and MacLaughlin and have found that both theories can adequately describe our results for the initial slopes(dTc/dnl)0 and concentration dependence ofTc. In particular, from the theory of Rivier and MacLaughlin, we have found characteristic temperatures for these alloys which are in agreement with those obtained from measurements on other physical parameters.