Objective: To identify determinants of nutrition guidance practices of general practitioner-trainees (GPtrainees), to investigate whether these determinants differ from those found by experienced general practitioners; to reveal educational directions towards the development of computer-based instruction on nutrition. Design: Cross-sectional study by means of validated questionnaires. Subjects: All GP-trainees in training at the eight university departments for vocational training in the Netherlands in September, 1998 (n 985). Main outcome measures: Reliability of determinants of nutrition guidance practices was calculated by means of Crohnbach's alpha. The mechanism of action of determinants was identi®ed by means of linear structural relationship analysis (LISREL) using a model developed for GPs. Results: Crohnbach's alphas for factors ranged from 0.58 ± 0.90. The empirical GP-trainee-data ®tted with the corresponding GP-model on the mechanism of action. Conclusions: The same predisposing factors, driving forces and barriers as found with GPs were identi®ed with GP-trainees. Comparing the GP-and GP-trainee-models, only minor differences were found in the path coef®cients between factors. Lack of nutrition training and education proved to be of great in¯uence on the extent of nutrition information given. The GP-trainee-model will be of use in developing computer-based instruction on nutrition. It is expected that GPs may also bene®t from this instruction.