The National Basketball Association (NBA) and National Hockey League (NHL) are studied to ascertain the determinants of betting volume on an individual game-to-game basis. Actual betting volume was obtained and aggregated across three on-line sportsbooks for the 2008-09 season. Independent variables such as the quality of teams, television coverage by network, day of the week, time of day, month of the season, etc. are included in a regression model to determine the factors that influence betting volume. The results reveal betting behavior is much like fan behavior as key fan-attributes, such as the quality of teams and the availability of television coverage, are shown to have a positive and significant effect on betting volume. The results imply that consumption plays a major role in the decision to gamble on sports. Pure investment-based gambling appears to be the exception, rather than the norm. The implication of this result as it relates to models of sportsbook behavior is explored.