This study was performed to determine whether students who are trained in developing a personal formulary become more competent in rational prescribing than students who have only learned to use existing formularies. This was a multicentre, randomised, controlled study conducted in eight universities in India, Indonesia, the Netherlands, the Russian Federation, Slovakia, South Africa, Spain and Yemen. Five hundred and eighty-three medical students were randomised into three groups: the personal formulary group (PF; 94), the existing formulary group (EF; 98) and the control group (C; 191). The PF group was taught how to develop and use a personal formulary, whereas e the EF group was taught how to review and use an existing formulary. The C group received no additional training and participated only in the tests. Student’s prescribing skills were measured by scoring their treatment plans for written patient cases. The mean PF group score increased by 23% compared with 19% for the EF group ( p < 0.05) and 6% for controls ( p < 0.05). The positive effect of PF training was only significant in universities that had a mainly classic curriculum. Training in development and use of a personal formulary was particularly effective in universities with a classic curriculum and with traditional pharmacology teaching. In universities with a general problem-based curriculum, pharmacotherapy teaching can be based on either existing or personal formularies. [ABSTRACT FROM AUTHOR]