The ultrastructure of the cephalic cuticle of 6 of 7 representative genera of Stibonematinae (Eubostrichus, Catanema, Laxus, Robbea, Leptonemella, Stilbonema) is investigated using SEM and TEM techniques. Additionally, one species ofSpirinia (Spiriniinae) and one ofDesmodora (Desmodorinae) were studied for outgroup comparison. Most of the studied species show modifications of the cephalic cuticle. Furthermore, at least four different pathways have been developed to reinforce the head within Stilbonematinae. Species with a coarsely annulated somatic cuticle (Leptonemella sp.,Stilbonema majum, andDesmodora ovigera) developed a rigid, non-annulated cephalic capsule by modifying the main constructing element of the median zone, the “ring body.” In faintly annulatedLaxus oneistus, the annulated cephalic capsule results from a newly inserted “block layer” between the median and basal zone. The non-an-nulated cephalic capsule ofRobbea sp. is formed by both the block layer and the ring body element. The annulated capsule ofCatanema sp. stems from a doubled number of fiber layers within the basal zone. InSpirinia sp., only the amphidial region is strengthened in what could be termed an amphidial shield. All forms with cephalic capsules show mechanisms to keep the oral region pliable. OnlyEubostrichus topiarius lacks a reinforcement of the cephalic cuticle. A comparison with the literature is made to elucidate corresponding structures within the cephalic capsules of representatives of Desmodorida. It is demonstrated that the presence of a cephalic cuticle is of no systematic value above the genus level.