We model the emergence of organization forms in simultaneous
bidding for labor services among heterogeneous agents. What distin-
guishes our approach from prior work is that occupational choice and
job matching are determined simultaneously, so that the opportunity
costs of entrepreneurs are accounted for. Equilibrium ?rms are diverse
in size and organization; workers turn out endogenously to be com-
plements or substitutes. The organization designs are e¢ cient and
maximize complementarity between agents.