This paper studies thermoreversible gelation in two-component polymer mixtures (A/B) in which both polymers carry associative groups capable of forming reversible pairwise bonds. The type of association is classified into the following three main categories: (i) association of polymers within the same species (AA and BE); (ii) association only between the different species (AB); (iii) all associations allowed (AA, BE and AB). On the basis of a recent theory of associating polymers, we derive possible phase diagrams for interpenetrating networks, alternating networks, and randomly mixed networks corresponding to each category, with special attention to the interference between gelation and macroscopic phase separation. For all types, homogeneously mixed networks are most easily stabilized near the stoichiometric concentration where the total number of A associative groups in the mixture agrees with that of B associative groups.