Previous work provided indirect evidence that planarians undergo abstinence-induced withdrawal from cocaine. The present study's purpose was to determine if planarians display withdrawal signs and, if so, to quantify the behaviors. Planarians were soaked in cocaine then transferred to either the same cocaine concentration or cocaine-free water. Compared to the cocaine/cocaine group, the cocaine/water group displayed a significant number of atypical behaviors, providing direct evidence of a 'withdrawal phenomenon' in planarians.