The effect of the number of others present on the amount of food eaten was investigated in the Netherlands by studying spontaneous meal size in 50 free-living young males and females. Subjects recorded food consumption, number of others present, hunger, taste of the food, food availability, and atmosphere at each eating or drinking moment for four (n = 30) or seven consecutive days (n = 20). The results of the study with four and the study with seven recording days were comparable. The mean Pearson within-person correlation coefficient between the number of other present and meal size was 0.24 (n = 50, p < 0.05). This correlation was significant for breakfast (0.40, p < 0.05) and snacks (0.18, p < 0.05), but not for lunch (r = 0.19, p > 0.05) and dinner (r = 0.15, p > 0.05). A path analysis showed no direct effect of the number of others on meal size, but revealed that social facilitation of spontaneous meal size was mediated by meal duration.