Cryptosporidium parvum is a coccidian agent of diarrhoeal disease affecting many mammals, including dairy calves. Calves infected with this enteropathogen may either be asymptomatic or manifest mild to profuse diarrhoea and dehydration. Keeping in view the importance of Cryptosporidium parvum in dairy calves, the current study was conducted to find out the prevalence in dairy calves, in and around Lahore and also to find out the most effective therapeutic measure to control the infection. For this purpose, 500 faecal samples (n=250 cow calves, n=250 buffalo calves) from different dairy farms and home-bred dairy calves were collected and analyzed by using faecal floatation method and modified Ziehl-Neelsen staining technique. Overall, 25.6% Calves were shedding C. parvum with a slightly high infection rate in the cow calves 27.2% than buffalo calves 24%. The highest infection rate was recorded in 1-30 days age group of dairy calves as 50.81% and 42.02% in the cow calves and buffalo calves, respectively. The infection rate of C. parvunm in the dairy calves of cow breeds indicated relatively high infection rate in crossbred cow calves (28.18%) than the Sahiwal cow calves (20%) and Nih Ravi buffalo calves (24%). The pattern of oocyst shedding was negatively correlated with increase in age, highest in the 1-30 days age group and lowest in the age group ranging from 9 months to 1 year and above. Diarrhoeac calves were infected significantly higher than the nondiarrhoeac calves indicating a direct relationship of diarrhea with C. parvum infection. Diarrhoea was the highest contributing factor to infection in 1-30 days age group with 58.97% infection rate in both the cow calves and 48.88% in buffalo calves than the nondiarrhoeac calves of the same age group as 36.36% and 29.16%, respectively. The infection rate was not associated with the sex of the dairy calves and the infection rate was almost equal in both the sexes. The cumulative rate of infection was relatively high (30.28%) in the physically healthy calves than weak (21.5%) and emaciated (19%) calves. Milk suckling calves were infected almost two times more than the ones utilizing both milk and fodder and almost 7 times of the fodder eating calves. The calves kept on dirt yards were infected more (28%) than the ones on the paved floor (21 .11%). A significantly high infection rate was observed in the cow calves and buffalo calves having some sort of contact with birds, rodents, dogs and cats (31.3%) and (25.80%) respectively, than the calves having very little or no contact with birds, rodents, dogs and cats as 19.27% and 12.12% in cow calve and buffalo calves, respectively. The results of the comparative efficacy of a.zithromycin and cotrimoxazole and kalvangi showed that azithromycin was the most effective of the three in treatingcryptosporidial infection in dairy calves under field conditions. It resulted in significant reduction in the oocyst shedding and consequently, better weight gain compared with kalvangi and Cotrimoxazole. The efficacy of Kalvangi in weight gain compared with kalvangi and Cotrimoxazole. The efficacy of Kalvangi in weight gain may be due to its vitamins, enzymes and Nigellone and Thmoquinone acting as an immune system booster. The results of Azithromycin in the present study on the overall weight gain of calves was significantly higher than the other two drugs used in the study suggesting it as a drug of highest efficacy.