Irrational prescribing originates in undergraduate therapeutics education, where prescribing skills have been overlooked. P-drug, a rational prescribing approach, has been developed in response to poor prescribing. In 2004, the first cohort of PBL final year students at Nelson R. Mandela School of Medicine reported feeling unprepared to prescribe medicines and requested help. We aimed to assist students in improving their prescribing competence and confidence. Students were tested and asked to rate their confidence for some of their responses. A stratified sample of 10 of these students, were interviewed, where they prescribed treatment for 4 paper cases. A week-long intervention was designed, covering key areas of weakness and prescribing skills and employing several learning strategies. Students evaluated the course, rating how they felt key competences changed. Test results averaged 47%. True/false questions were better answered (69%) than short answer questions (21%), the worst of these testing drug level interpretation (48%) and dosage calculation (5%) respectively. Students interviewed gave appropriate treatment for 4 of 40 cases and important patient information in only 1 case. Eight students gave an appropriate text for further information. The student evaluation showed an improvement for all prescribing abilities. (Contains 4 tables.)