Nematodes were found to be abundant in a collection of Cladonia glauca from Ireland. Irregular tuberculate galls on the podetia were probably due to a species tentatively referred to Nothanguina. Aphelenchoides lichenicola sp. nov. and Ottolenchus cabi sp. nov. are described; the former may feed on the fungal component, while the latter probably parasitizes the algal partner. The separation of Ottolenchus from Tylenchus is discussed and six new combinations into Ottolenchus are proposed. Further nematodes found in the sample included species of the genera Belondira, Chilwoodius and Discotnyctus (all Dorylaimida), and a juvenile Rotylenchulus (Hoplolaimidae); this last probably a contaminant. These observations on a single collection suggest that lichens may have a rich and specialized nematode fauna.