Rate constants for the reactions of Si (P-3, ID, and IS) atoms with SiH4 have been determined using a combined laser photolysis/laser induced fluorescence technique. The reaction of Si(P-3) with SiH4 is shown to proceed with a rate constant k(Si(P-3(J)) + SiH4) = (2.1 +/- 0.2) x 10(-10) cm(3) molecule(-1) s(-1), with no discernible pressure dependence over a pressure range of 5-20 Torr of N-2 diluent. The rate constants of each triplet component of Si(P-3(J=0,1,2)) atoms exhibit no significant spin-orbit dependence within the experimental uncertainties. The results of the density functional theory calculations show that the reaction of Si(P-3) atoms with SiH4 proceeds via a loose transition state. The Si(ID) + SiH4 reaction rate constant is determined to be (5.2 +/- 0.3) x 10(-10) cm(3) molecule(-1) s(-1). The Si(S-1) atom is less reactive with SiH4 than the Si(D-1) atom, with an upper limit of k(Si(S-1) + SiH4) = 4.7 x 10(-13) cm(3) molecule(-1) s(-1).