The double immunofluorescence technique was used to examine the distribution and interrelationship between LENK- and VIP-immunoreactive nerve fibres within the muscle layer and myenteric plexus of the large intestine in a young female patient (aged 17 years) suffering from colitis ulcerosa activa (CUA). As the CUA was found to be totally drug-resistant, a pancolotomy was performed by means of the Soave technique. Varicose nerve fibres, immunoreactive either to LENK or VIP, but not to both substances simultaneously, were found in all fragments of the bowel studied. A striking feature was their distribution pattern within the studied layers. In all cases LENK-IR fibres were closely accompanied by VIP-IR terminals. The density of the examined fibres depended on the bowel fragment studied, and was the greatest in the sigmoid colon, descending colon and rectum, while the lowest number was found in the caecum. The results of the present study may thus be indicative for the involvement of LENK- and VIPIR nerve fibres in the control of bowel functions during CUA, possibly on the basis of a "cross-talk" between terminals running in close vicinity to each other.