The effect of Asa foetida (0.1% alcoholic dilution) and a combination of Asa foetida and Nux vomica (0.01% alcoholic dilution) was tested in a multicenter placebo-controlled double-blind trial. Both groups with active medication differed trivially but showed a marked superiority to the placebo group. The differences, however, just miss the conventional 5%-level of statistical significance. For the interpretation of this result it must be considered that only about half of the total of patients could be reached who in the planning phase of the study had been regarded necessary for a statistical confirmation of a therapeutic effect. The diagnosis "Colon irritabile" is discussed in its historical context and the psychological structure of the patient sample is described by means of the scores of a standard personal inventory test (FPI). The trial shows that it is possible to obtain objective results on the basis of the patients' judgment (rating scales with low information content).