Two isolated jejunal segments (Thiry-Vella (T-V) loops) were created in 7 dogs. One contained a 'wide' cycloperistaltic (C-P) segment while the other, acting as a control, did not. The C-P segment had the same diameter as the jejunum. Fluid perfusion experiments showed that there were no changes in the volume of output, absorption and pooling of the fluid in the T-V loops containing the 'wide' C-P segment. This was in contrast with significant changes shown in earlier experiments using 'narrow' C-P segments.