This study was conducted to investigate the prevalence of parasitic protozoan agents in lambs with diarrhoea in the Van province (Eastern Turkey). Faecal samples from 132 diarrhoeic lambs aged from one day to two months old were collected at 12 different herds from January 2005 to May 2005. The faecal samples were examined by using, native-Lugol, Fulleborn's salty water technique, and a Modified Ziehl-Neelsen staining technique for Cryptosporidium. The parasitological examination revealed that 98 (74.24%) of the lambs were infected with one or more of parasitic protozoan agents. Eimeria, Giardia, and Cryptosporidium were detected in 80 (60.60%), 64 (48.48%), and 18 (13.63%) of the lambs, respectively. According to statistical analysis, Eimeria sp. oocysts were significantly higher (P<0.01) in lambs aged between 31 and 60 d (76.81%, 53 of 69) than in those of 16-30 d of age (50%, 21 of 42) and 1-15 d of age (28.57%, 6 of 21). There were significant differences in Giardia prevalance when lambs of 1-15 d of age were compared with those 16-30 d of age (P<0.05). Statistical analysis revealed that Cryptosporidium sp. oocysts were significantly higher (P<0.01) in lambs aged between 1 and 15 d (66.66%, 14 of 21) than in those of 16-30 d of age (4.76%, 2 of 42) and 31-60 d of age (2.89%, 2 of 69). Moreover, Giardia sp. and Eimeria sp. showed significant co-occurrence (34.84%). The results obtained confirmed the fact that protozoan infections are widespread in diarrhoeic lambs in this geographical region.