Roller mutants of Caenorhabditis elegans rotate around their long axis and move in circular paths. Isolation and sequence of the rol-6 gene of C. elegans have shown that it encodes a cuticle collagen. In this paper, we describe the morphological alterations seen in the cuticle of the right roller mutant rol-6 (su1006) at the ultrastructural level. Deep-etched replica analyses showed that the honeycomb elements, fibers organized in a pentagonal fashion above the fishbone fibrous layer, completely fill the intermediate layer, which is observed to be largely empty spaces in the wild-type strain. The honeycomb fibers appear to connect the cortical and basal regions of the mutant cuticle. These fibers are likely to be involved in generating the helical twist of the mutant animals. Deep-etched replicas also revealed a delicate network of filaments on the nematode surface.