We have studied the structure of aggregates formed by oppositely charged polyelectroytes of the same chain length N and charge density and the kinetics of the formation of these aggregates using a dynamic Monte Carlo algorithm. The model considers the evolution of chains through local motion of monomers and exhibits the complex behavior associated with the formation of such aggregates. The chains interpenetrate in two distinct steps-the chains first diffuse toward each other and then collapse abruptly to form smaller aggregates. This abrupt collapse is a consequence of cooperativity in the aggregation process. The chains collapse and are considerably smaller in the aggregate than in isolation; the conformational properties of each of the two chains of the same chain length and charge density in the aggregate are the same. The radii of gyration of the chains in the aggregate and of the aggregate scale as N1/2. Aggregates formed by longer chains initially scale as N. These aggregates continue to reorganize and eventually scale as N1/2. However, it is possible that for sufficiently long chains, as in real experimental situations, this process of reorganization is hindered by the formation of entanglements, etc. The aggregates would then form a nonequilibrium structure and would not scale as N1/2.