The electrical resistivity σ of the intermetallic compounds Gd(Al 1− x M x ) 2 with M In, Ga, Pd, Sn, Si and Ge was measured, in the range of x giving the C15 crystal structure, between 4.2 and 300 K. The Curie temperatures T c and the resistivity contributions ρ s due to disordered magnetic moments of Gd above T c were observed to depend sensitively on x. This dependence was not so strong in the case of M In and Ga, which are isoelectronic with Al, as in the case of the other M. In general it was found that the variation of T c( x) and ρ s( x) for a given M has a similar character. While the dependence on x of T c can be explained already by changes in the total density of states at the Fermi level E F on alloying, the dependence on x of ρ s points to the importance of the normalized partial density of states components n 1 for different angular momenta l at E F, in combination with the corresponding l-f exchange matrix elements. In accordance with the existence of such drastic band structure effects on alloying, it was found that the dependence on x of the residual resistivity ρ, does not follow the Nordheim rule ρ r ∼ x(1− x).