Aromatic aldehydes are smoothly converted into the corresponding acylals in good yields in the presence of 0.10 mol% Bi(OTf)3•xH2O. Ketones are not affected under the reaction conditions. The highly catalytic nature of bismuth triflate and the fact that it is relatively non-toxic, easy to handle and insensitive to small amounts of air and moisture makes this procedure especially attractive for large-scale synthesis.