The Luria-Das Information Processing Model of human learning holds that information is analysed and coded within the brain in either a simultaneous or a successive fashion. Simultaneous integration refers to the synthesis of separate elements into groups, often with spatial characteristics; successive integration means that information is processed in a serial order, so that information is surveyable only in a temporal, orderly manner, with knowledge of each bit of information dependent on the previous bit. To investigate the relationship betwen simultaneous-successive processing and academic achievement, undergraduate college students (N=157) completed six processing tasks: the Raven Progressive Matrices, memory for design, and figure copying (indices of simultaneous processing); and free recall, serial recall, and digit span-forward (indices of successive processing). Students' task scores were then compared with their cumulative grade point average (GPA) and American College Testing (ACT) composite scores. Analyses of results indicated that the level of simultaneous and successive processing was related systematically to GPA; high levels of both processing modes were necessary for high GPA achievement. Simultaneous processing seemed relatively more important than successive processing for high ACT performance, perhaps due to the ACT's emphasis on complex reading. (WAS)