SIMCOL is a program for investigating questions concerning the determinants of coalitional behavior. One major criticism of the typical Vinacke and Arkoff (1957) procedure is that this game situation allows uncontrolled personality variables to have an effect on the coalitional behavior, since all players are face-toface throughout the experiment (Chertkoff, 1971; Rapoport & Kahan, 1974). Also. there are large practical difficulties involved in recruiting and running large numbers of experimental groups to examine the effects of experimental manipulations on the coalitional bargaining process and its final outcome (psathas & Stryker, 1965; Stryker, 1972). The typical random assignment of weights or power to players may restrict the external validity of the bargaining process under investigation. SIMCOL controls for the effect of personality variables, since two of the three players in the triad are simulated. Large numbers of groups are not required. The assignment of the weights or power of each member of the triad may be reported to players as either random or as based upon their performance on a pretask. This pretask consists of a number of simulated prisoner's dilemma game (pDG) trials with a tit-for-tat strategy employed by the simulated other player. A single power distribution is available where A > B > C and A < (B +C). Players may be assigned to any of the three power positions, with the other two players being simulated. Program Input. SIMCOL accepts six input parameters. The first two parameters accommodate a threecolumn ID field and a single column for sex. The third input parameter assigns the player to the A, B, or C position in the triad along with that position's associated weight. The fourth input parameter determines whether or not the subject will play 10 PDG tit-for-tat trials prior to the triadic situation. The fifth parameter determines whether the player will be informed that the weights are assigned on the basis of performance in the last game (PDG trials) or randomly. The sixth parameter determines the number of bargaining trials that will be involved in the player's bargaining with his preferred partner concerning reward division. Output. SIMCOL outputs the six input parameters, the subject's initial PDG choice, the number of cooperative choices made in the PDG situation. the subject's partner preference. initial bargaining demand, subsequent bargaining demands, and the subject's final bargaining demand. Language and Computer. SIMCOL was written in FORTRAN IV and was developed on a DEC System-IO time-share system. Limitations. Only a single triadic power distribution is available. Players are run through only one game since the average session requires 30 min per subject. Two diagrams, external to the program, are required: the PDG payoff matrix and the triadic board game (both were adapted from Vinacke, 1969). Availability. A listing of SIMCOL is available without cost from John F. Flaherty, Department of Psychology, Huntington Hall, Syracuse University, Syracuse, New York 13210. --