The efficacy and safety of the standardized herbal combination preparation of Enteroplant, consisting of peppermint oil (90 mg) and caraway (50 mg) in an enteric coated capsule, have been studied in a double-blind, placebo-controlled multicentre trial in patients with non-ulcer dyspepsia. A total of 45 patients were included in the trial after thorough physical and gastro-enterological examination. The primary outcome variables were the change in the intensity of pain and the global clinical impression (Clinical Global Impression [CGI], Item 2), which were evaluated for 39 patients (test preparation: 19, placebo: 20). After four weeks of treatment both target parameters were significantly improved for the group of patients treated with the peppermint oil/caraway oil combination compared to the placebo group (p = 0.015 and 0.008, respectively). Before the start of treatment all patients in the test preparation group reported moderate to severe pain, while by the end of the study 63.2% of these patients were free of pain. The pain symptoms had improved in a total of 89.5% of the patients in the active treatment group. After 4 weeks the Clinical Global Impressions were improved for 94.5% of the patients treated with the peppermint oil/caraway oil combination. The trial medication was also superior to placebo with respect to pain frequency, medical prognosis, the severity of the disorder and the efficacy index (CGI, Items 1 and 3), which were adopted as secondary end-points for evaluation of efficacy. There were similarly favourable findings for the herbal combination, compared with placebo, with respect to the reduction of other gastrointestinal symptoms. The combination preparation was found to be excellently tolerated. There was a total of 7 adverse events (test preparation: 4, placebo: 3), with a causal association with the treatment being ascribed in one case for the test preparation group and one case for the placebo group.