Two homeopathic pathogenetic trials (HPTs, provings), of identical design were conducted: of Acidum malicum 12 cH and Acidum ascorbicum 12 cH. Each trial included 20 healthy volunteers. Both were of double-blind, placebo-controlled, randomised, four period crossover design, with two sequences. 'Healthy' was defined in terms of SF-36 scores, medical judgement and blood tests. All volunteers had regular interviews with the same supervisor. No serious adverse reactions occurred. The causal relationship of each symptom with treatment was judged, blind, by the volunteer, the supervisor and a 9-item pathogenetic index. For Acidum malicum 79 symptoms were identified by the supervisor, 57 were included in the final analysis, 22 occurred in verum treatment periods. For Acidum ascorbicum, of 55 symptoms, 39 were included in the analysis. 16 occurred in verum treatment periods.