A double scenario characterizes the epidemiology of HIV infection in children. In countries where highly active antiretroviral therapy (HAART) is available, the pattern of HIV infection is evolving into that of a chronic disease, for which control strictly depends on patients' adherence to treatment. In developing countries with no or limited access to HAART, AIDS is rapidly expanding and is loaded with a high fatality ratio, due to the combined effects of malnutrition and opportunistic infections. The digestive tract is a target of the disease in both settings. Opportunistic infections play a major role in children with severe immune impairment, with Cryptosporidium parvum being the leading agent of severe diarrhea. Several therapeutic approaches are effective in reducing fecal output, but the eradication of the parasite is rarely obtained. Other opportunistic infections may induce severe and protracted diarrhea, including atypical mycobacteria and cytomegalovirus. Diagnosis of diarrhea should be individually tailored based on presenting symptoms and risk factors. A stepwise approach is effective in limiting patient discomfort and minimizing the costs of investigations, starting with microbiologic investigation and proceeding with endoscopy and histology. Aggressive treatment of infectious diarrhea is required in severely immunocompromised children. However, antiretroviral therapy prevents the development of severe cryptosporidiosis. The liver and pancreas are also target organs in HIV infection, although functional failure is rare. The digestive-absorptive functions are impaired, with steatorrhea, nutrient malabsorption, and increased permeability occurring in 20-70% of children. Intestinal dysfunction contributes to growth failure and further immune derangement, leading to wasting, the terminal stage of AIDS. Nutritional management is crucial in HIV-infected children and is based on aggressive nutritional rehabilitation through enteral or parenteral routes and micronutrient supplementation.HIV may play a direct enteropathogenic role and is implicated in both diarrhea and intestinal dysfunction. This explains the efficacy of antiretroviral therapy in inducing remission of diarrhea and restoring intestinal function. Gastrointestinal side effects of antiretroviral drugs are increasingly observed; they are often mild and transient. Severe reactions are rare but require the withdrawal of drugs. In conclusion, severe enteric infections and intestinal dysfunction characterize the intestinal involvement of HIV infection. This is more common in, but not limited to, children who do not receive effective antiretroviral therapy. Diagnostic approaches include microbiologic and morphologic examinations and assessment of digestive processes, but immunologic and virologic data should be also carefully considered. Treatment is based upon specific anti-infectious drugs, antiretroviral therapy, and nutritional rehabilitation.