Patients take nitazoxanide daily for 8 weeks with a dose escalation after the first 4 weeks. Patients return to the hospital for examinations every 2 weeks during the 8-week treatment period and 6-week follow-up. Nitazoxanide therapy is discontinued in patients showing a complete clinical and parasitologic response (therapeutic cure) after 8 weeks of treatment and in patients showing a therapeutic cure at two consecutive visits (Weeks 2 and 4 or Weeks 4 and 6). These patients undergo a physical examination including stool analysis for Cryptosporidium parvum oocysts and routine laboratory tests at Weeks 2, 4, and 6 after completion of nitazoxanide therapy. Patients who do not show a complete clinical and parasitologic response (therapeutic failure) after 8 weeks of treatment are allowed to remain on nitazoxanide therapy through the Open Label Compassionate Use of Nitazoxanide in Treatment of Cryptosporidiosis in AIDS Patients (UMD-95-009) protocol.