The present study was planned to elucidate the in- fluence of dexamethasone administration of Cryptosporidium oocysts output, body-weight gain, organs weight, total and electrophoretic patterns of serum proteins in chickens infected with Crytosporidia. The results revealed the following findings and conclusions: 1- The maximal body weight gain was observed in case of non-infected control chickens. Severe retardation of weight gain was recorded in infected group and infected chickens treated with DEX. 2- The minimum Cryptosporidium oocysts output was recorded in control chickens, while there was a Significantly higher total oocysts output in infected chickens treated with DEX. 3- There was a significant decrease in weight of spleen, bursa of Fibricius and thymus of chickens in both groups of infected and infected treated with DEX. The lowest weight of these organs was noticed in infected chickens treated with DEX. Total proteins, albumin, alpha, beta and gamma globulins decreased significantly in infected chickens treated with DEX, while there was a significant increase in albumin and gamma globulin in the group of infected chickens. The A/G ratio of infected and DEX treated groups was less than in control.