Giemsa-stained blood smears were examined from 70 deep demersal fish of 27 species in 20 genera, trawled from depths of 747–4143 m in the region of the Porcupine Seabight, north-east Atlantic. Infections were found in four species of teleosts in three families: 1/3 Alepocephalus rostratus and 1/3 Narcetes stomias (Alepocephalidae); 2/3 Antimora rostrata (Moridae); and 1/1 Cataetyx laticeps (Bythitidae). Blood films from C. laticeps and Antimora rostrata were well preserved but those from the other two species were less satisfactory. The blood parasites included two types of haemogregarines, Haemohormidium-like and viral erythrocytic necrosis (VEN)-like infections. Haemogregarina (sensu lato) johnstoni sp. nov. was described from C. laticeps captured at 1541 m. This haemogregarine was unusual in apparently having dimorphic gamonts, some with prominent caps. A second, but monomorphic, haemogregarine found in Alepocephalus rostratus captured from 985 m, was named as Desseria sp. since only extracellular stages were observed. Haemohormidium-like organisms were found in Antimora rostrata taken from 2441 m, and were similar to those described previously from this deep-sea fish. A VEN-like infection from one N. stomias captured from 2567 m was reported. No marked effects on host cells were evident in any of these blood infections.