The pattern of use of khat (Catha edulis Forsk), alcohol, cigarettes and tranquillizers among 479 medical and paramedical students in a boarding college in northwestern Ethiopia was studied by an anonymous self-administered questionnaire. The survey coverage rate was 98.8%. The majority of students were males (82.6%) and their average age was 21.2 years. The prevalence rate of current use of alcohol, cigarettes, khat and tranquillizers was 31.1%, 26.3%, 22.3% and 7.7%, respectively. These substances were also used in combinations, the most frequent involved khat, alcohol and cigarettes. Use of khat varied by the type of training (medical/paramedical) and by phase of medical education (preclinical/clinical). These variations were also apparent when data were analysed by sex and frequency of khat use. It appears that the pattern of khat use among university students is similar to that reported for substance abuse in other countries. Because of the economic importance of khat in the Ethiopian economy, its control may be difficult at present.