Both Nevin (1969) and Shimp (1966) found on different choice procedures that pigeons equate (match) the proportion of their choices to the proportion of reinforcers each choice delivers. Their results differed in terms of the order of successive choices: Shimp found pigeons ordered successive choices so as to maximize the reinforcement rate, whereas Nevin found no evidence of such an ordering. Experiment 1 replicated both studies and found in both: (a) matching relations and (b) sequential dependencies of choice that corresponded with Shimp's maximizing prediction. The next three experiments studied the order of choices in three other choice procedures: (a) concurrent variable-interval schedules with a changeover delay, (b) concurrent variable-interval schedules without a changeover delay, and (c) concurrent-chains schedules. In all of these procedures, control of choice at the level of the response sequence was evident. The major features of the data from all four experiments were attributed to two molecular processes: response perseveration and reinforcement maximization. This evidence for a microstructure of choice suggests that the molar matching law is not isomorphic with the molecular processes governing concurrent performances.