['The present study assessed whether cigarette smokers who are also regular khat users would demonstrate greater impairments in verbal learning and recall compared to both non-smokers who are khat users and control subjects.', 'An independent-measures, between-subjects design with two covariates.', 'An out-patient, university research center in Taiz, Yemen.', 'Subjects were 175 Yemeni college students (90 men, 85 women) ranging in age from 18 to 38 years. Seventy-five subjects were self-reported chronic cigarette smokers and khat users, 48 non-smoking subjects were self-reported to be chronic khat users and 52 non-smoking subjects reported no current use or history of khat use.', 'Verbal learning and verbal memory recall was assessed by subject performance on the Arabic version of the Rey Auditory Verbal Learning Test (RAVLT).', 'Statistically significant differences (P < 0.05) were observed in RAVLT acquisition learning trials 2-5 and on delayed recall measures between concurrent khat and cigarette users compared to both the khat-only group and the control group of non-users of khat and cigarettes. On each of these trials, concurrent users recalled fewer words, demonstrating a slowed rate of verbal learning. This same pattern of performance was also seen on delayed recall measures. Khat use alone did not affect immediate or delayed recall of previously learned words.'] Is concurrent use of khat and tobacco associated with verbal learning and delayed recall deficits?