The Social Facilitation Effect shows performance on many simple tasks is enhanced by crowds of onlookers or co-actors (others performing the same activity). Previous experimental research has shown that Electronic Gaming Machine (EGM) betting behavior is intensified by the belief that others are gambling along with the subject (Rockloff and Dyer, J Gambl Stud 23(1):1-12, 2007). The present study extends these findings by simulating crowds of differing sizes using a fake video-conference along with a live confederate who gambles concurrently with the subjects. Fifty-four male and 81 female subjects aged 18-82 (M = 46.9, SD = 16.7) played a laptop simulated 3-reel EGM using a $20 stake in 3 conditions: (1) alone, (2) in a simulated group of 5 persons plus 1 live confederate, or (3) in a simulated group of 25 persons plus 1 live confederate. The EGM outcomes were rigged with a fixed 20 trial winning sequence followed by an indefinite losing sequence. As hypothesised, gambling intensity, as measured by trials played, speed of betting and final payouts, was progressively greater with larger crowd sizes (P < .05). In contrast, bet-size was slightly lower with larger crowds. The results suggest that gambling venues with more players tend to increase gambling persistence and contribute to greater long term monetary losses.