We studied xerostomy and its correlation with periodontal and dental cavity diseases in HIV patients, through measurement of salivary flow and through variables such as saliva buffer capacity, salivary pH, periodontal index, MDF index, dental carie risk and risk of periodontal disease. One hundred patients were analyzed. They were distributed into two groups: Group I (test) -50 patients evidently HIV + , from whom information was collected and analyzed regarding age, gender, skin color, habits, general and oral diseases, levels of T-CD4 lymphocytes, viral load and highly active antiretroviral therapy (HAART); and Group II -(control) 50 HIV -patients, from whom information was collected and analyzed regarding age, gender, skin color, habits, general and oral diseases. In both groups, measurement of salivary flow, pH and buffer capacity was made. Group I presented high MDF, bacteria plaque and bleeding, with a greater susceptibility to the risks of oral cavities and periodontal disease. The salivary flow and the buffering capacity of the saliva were low, indicating a high level of xerostomy. Two important modifying factors influence these pathologies in an incisive way: one is immunossuppression and the other is HAART therapy. The control exhibited results that are closer to normality; it had better oral-health conditions.