Pentacyclic triterpenoids exert their antitumor activity through different mechanisms, one of which is apoptosis induction. Although there are many reports on the apoptosis inducing activity of pentacyclic triterpenoids, a systematic survey and discussion on their structure-activity relationships (SARs) is still lacking. In this review, we summarized such activity of oleanane, ursane and lupane type triterpenoids, the most abundant pentacyclic triterpene prototypes in plants. Their structural characteristics responsible for the activity are also discussed, in order to unravel their SARs for the apoptotic induction and benefit further investigations on the antitumor triterpenoids.