Previous studies on WOM have stressed the importance of peer consumer reviews in making purchase decision. When people follow the others purchase decision on the Internet, online herd behavior occurs. This paper presents three experiments that examine herd behavior in virtual communities: In experiment 1, a 2 (Volume: sales/recommendation) online experiment was conducted. Experiment 2 investigated herd effects using a 2 (Number of volume: relative/absolute)　×　2 (Number of scale: large/small) online experiment. Online experiment 3 examined herd effects using a 2 (Number of experience-sharing messages: more/fewer) × 2 (Number of recommendations: more/fewer) online experiment. These experiments involved 484 people in a Taiwanese virtual community. Results demonstrated that consumer recommendation volume causes significantly more frequent online herd behavior compared with sales volume. This study advances the literature on online herd behavior in virtual communities.