Since the publication of James Buchanan's (1965) seminal piece on clubs, club theory has been extended to consider such things as heterogeneous memberships, membership discrimination, institutional form, multiple overlapping generations of members, and game-theoretic aspects of stability (i.e. the existence of a core).' A little explored, but important, issue concerns the influence of uncertainty and risk attitudes on club decisions regarding provision, membership size and capacity. This omission is indeed unfortunate because club members often face uncertainty with respect to the actual congestion they will experience during those times when they attempt to use the jointly shared facility. Many important examples of clubs, such as military alliances, communities, communication networks and transportation systems, experience random use, thus leading to the type of uncertainty analysed here. Uncertainty can affect clubs, their members and potential members in at least five ways. First, a potential member may be uncertain as to whether he will be admitted to membership; membership slots are limited, and not all individuals seeking membership are therefore successful. Second, a member may be uncertain as to the availability of the facilities during a given visit; capacity constraints may keep some members from utilizing the facilities. Third, members may not know the exact monetary costs of club participation, and, fourth, members may not know the degree of congestion during a particular visit. Fifth, uncertainty may characterize clubs on the supply side; facilities may suffer operational difficulties owing to poor maintenance, overuse or breakdowns. Hillman and Swan (1979, 1983) have examined the first type of uncertainty, whereas De Vany and Saving (1977) have analysed supply-side uncertainty for the trucking industry by treating both highway maintenance and demand as stochastic. De Vany and Saving (1977, 1980) have also calculated congestion tolls for highways where traffic is random and no capacity constraint exists (i.e. additional cars can always enter the roadway). In a working paper, McCormick and Adams (1983) have investigated the second and fourth types of uncertainty, but their model departs significantly from the analysis here by assuming risk neutrality and by utilizing queuing considerations. The model here incorporates uncertainty regarding a member's utilization of the shared facility, a member's fee payments and the degree of congestion experienced during a visit; hence, uncertainty cases two, three and four above are addressed. The analysis differs from all previous uncertainty club models