Rectosigmoid electric control activity and intraluminal pressure were measured in the fasting state and after a standard 3040-kJ meal in irritable bowel syndrome (IBS) patients (n = 41), diverticulosis patients (n = 15), and healthy controls (n = 13). Analysis of myoelectric and motor patterns was performed computer-based with home-made software. Spectral analysis (fast Fourier transform) and computer recognition of slow waves emulating visual scoring showed very similar slow-wave frequency patterns in all three groups. Calculation of contractile indices displayed a widely scattered variable of motility in all three groups without significant differences. IBS subgroups with different bowel patterns showed very similar frequencies of basic myoelectric rhythm and a considerable overlap of contractile activity without significant differences among the subgroups and compared with controls. Slow-wave rhythm seems unlikely to be the basis of disturbed motility in IBS and diverticular disease. A specific pattern of contractile activity was not detectable in either condition.