Number- and weight-average molecular weight of condensation polymers formed by primary molecules carrying different species of functional groups {A(i)} (i = 1, 2,.., s) are derived by cascade theory. These functional groups are allowed to form multiple junctions of variable multiplicity k. The gel point condition is found to be given by Sigma w(i)/(μ) over bar (pi,i) + 1/Sigma f(i) - 1 = 0, where f(i) is the number of A(i) groups specified by the index i on a primary molecule, w(i) equivalent to f(i)/Sigmaf(i) f the number fraction of the species i it carries, and (μ) over bar (w,i) the weight average multiplicity of the junctions formed by the groups A(i). The explicit form of the molecular weight distribution function is found for the simplest case of two components. Possible application to thermoreversible gelation is suggested. (C) 2003 Wiley Periodicals, Inc.