Concerned with explanation and prediction of legislative decision-making, this thesis was based on the premise that relatively structured, discernable patterns of behavior underlie the everyday decisions made by legislators. It has focussed on the final stage of legislative decision-making, the recording of preferences on roll call votes, and has tested the hypothesis that legislators form voting groups as they take voting "cues" from each other.Using "Q" factor analysis, the roll-call voting of the 1971 Session of the Indiana Senate was examined and five voting groups were found. The voting groups were named according to casual inferences made by the researcher.The implications of the findings of this thesis were discussed and specific suggestions for further research were presented.