The cytology of the nervous tissue of the metacestode of Hymenolepis microstoma was studied by electron microscopy. The small (3–5 μm) nerve cell bodies are smooth to irregular in outline, possessing one to several neurites that form synapses in the neuropile. Each neuronal perikaryon contains a single nucleus with a single nucleolus, numerous free ribosomes, occasional polyribosomes, small numbers of β-glycogen granules, multivesicular bodies, mitochondria, complex (coated or alveolate) vesicles, one or more Golgi complexes, and variable numbers of vesicles. Microtubules and microfilaments, however, are absent from the perikaryon. Subsurface cisternae are well developed; the inner faces of them are studded with ribosomes. Five types of vesicles, believed to contain neurotransmitter and (or) neurosecretion were identified on the basis of vesicle osmophilia and size distribution. On the basis of vesicle content, four nerve cell types were identified: sensory neurons, two putative interneurons, and one neuronal type possessing characteristics of both interneurons and motor neurons.