The present study was conducted on 290 buffaloes, 250 of them were newly-born calves, aged from one day to six months old, and 40 of them were adults, in the period from January to December 2004. These animals belonged to some private farms in El-Dakahlia governorate. The results of parasitological examination in the present study cleared that the infection rate of Cryptosporidium parvum was 19.65% (22.40% in animals less than 6 month age and 2.50% in adult ones). The clinical examination of the diseased animals infected with the parasite revealed no elevation in body temperature and presence of diarrhea of different degrees, anorexia, general weakness, unability for suckling milk with decreased of life animal body weight, also presence of variable state of dehydration with different degrees according to the infection rate. It was observed that the highest rate of infection was in calves aged from one day to one month old (32.38%), Highest rate of infection was in winter season followed by spring, autumn and summer (48.38%, 23.80%, 9.67% and 7.93%) respectively. Dealing with the biochemical changes, the study proved that there were significant decreases in total serum protein, albumin and globulin levels. The results of protein electrophoresis cleared that there was a high significant decrease in gamma globulins fraction when compared with control group as a result of general weakness and unability of the animals for suckling in this period which leads to decreased antibody needed for immunity against diseases. The study declared a high significant (P < 0.01) decrease in TRBCs and Hb. On the other side a significant (P < 0.01) increase in TWBCs and PCV in addition to presence of significant decrease in serum glucose, sodium, chloride and iron levels. On the contrary there were significant increase in blood serum urea, creatinine and potassium levels was evident. Sulphadimidine powder, ringers lactate solution in addition to New Diaclean were used for the treatment of the diseased cases. The study revealed that all the treated cases showed normal levels in their blood biochemical parameters after 10 days of treatment.