Incidence and geographical distribution of the cereal cyst nematode (CCN, Heterodera spp.) in winter wheat fields in Algeria. Cereal cyst nematodes (CCN, Heterodera spp.) are the most damaging plant-parasitic nematode species on wheat, causing severe economic loss in global wheat production. In summer 2015, we analyzed samples collected from 22 wheat fields in Algeria using the Fenwick can technique. The study revealed that 54.55 % of wheat fields were infested with cereal cyst nematodes. The species was observed in several locations in the northern part of Algeria but not in the southern desert area. Population densities of CCNs in soil varied between the regions at an infestation rate of between 0.6 ± 0.54 and 86.6 ± 19.96cysts/500 g of dried soil. Furthermore, we found an average of 56.33 ± 15.18 and 364.70 ± 81.93 second-stage juveniles and eggs per cyst. The infestation was most severe in cereal fields in Draa Semar and Djendel with 86.6 ± 19.96 cyst/500 g of soil and 57.4 ± 17.55 cysts/500 g of soil, respectively. Infestation was lowest in fields in Ras Elouad, Sidi Mbarek and Sedraia with 0.6 ± 0.54 cysts/500 g of soil; 1.6 ± 1.67 cysts/500 g of soil and 2.4 ± 1.67 cysts/500 g of soil, respectively. Heterodera spp. was distributed throughout the cereal growing province in Algeria and could cause economic loss in these regions.