1,1,3,3-Tetra- and 1,1,1,3,5,5,5-heptamethyltrisiloxane used as model compounds for hydrosilylation of C8H16 and C16H32 allowed to select (i) [Pt(PPh3)(2)C2H4], (ii) H2PtCl6 in cyclohexanone, (iii) Karstedt's Pt complex [Pt-2{CH2=CHSi(Me-2)(2)O}(3)], and (iv) bis(1,5-cyclooctadiene)-di-(mu-trimethylsiloxy)di-rhodium(I) complex as promising catalysts. The (iii) was active and selective at 10(-5)-10(-6) mol Pt/(mol equivalent to SiH) to give products in 85-95% yield, but required 80-100degreesC for the reaction to run. The (iv) was active at 25-60degreesC, but only at 200 x 10(-6) mol Rh/(mol equivalent to SiH). Polyhydrosiloxane (Me)(3)[OSiMe2](m)[OSiHMe](n)OSiMe3(m/n = 50/25) catalyzed by (iii), reacted with allyl glycidyl ether and allyl methacrylate at 90degreesC, with allyl polyether at 100degreesC, and with C8H16 and C16H32 at 110degreesC; with (iv), the conversions were completed at 60degreesC and, at 10(-4) mol Rh/(mol equivalent to SiH), even at 20-25degreesC. Optimization runs with poly(hydro, methyl)siloxane resulted in quite similar reaction conditions. The olefin reactant had to be absolutely dry.