THis study examines a contingency relationship between task uncertainty and structure of project teams in conjunction with the leader-member communication patterns. Multivariate analyses are used to analyze the data from 63 R & D project teams of research laboratory in a large manufacturing corporation. Major findings for this study can be summarized as follows. First, project teams with an organic structure are found to yield high performance when task uncertainty is high, while project teams with a mechanistic structure achieve high performance when their tasks are relatively certain. Second, patterns of leader-member comunication are significantly associated with both task uncertainty and structural characteristics of project teams. This implies that leaders of project teams communicate with their members in more conslutative manner when their tasks are uncertain or when their team structure exhibits organic characteristics. Finally, task uncertainty playus a significant moderating role in the relationship between consultative communication patterns and performance of project teams. Based upon these findings, this study offers several theoretical, practical, and methodological implications.