Objective: To investigate the effects of Ramadan fasting on serum concentrations of immunoglobulin (Ig)G and IgM, and salivary IgA concentrations. Methods: Blood and saliva samples were collected one week before and during the last week of Ramadan from healthy male volunteers. Albumin, total lymphocyte count, electrolytes, and IgG and IgM concentrations were determined in serum; salivary IgA concentrations were measured. Anthropometric measurements were also recorded. Results: Samples were collected from 35 subjects (mean age 35.86 years, range 20-59 years). Weight, body mass index, albumin levels and the nutritional risk index decreased significantly during Ramadan fasting compared with before fasting. In addition, Na þ and Cl À electrolyte levels were significantly decreased during Ramadan. Serum IgG concentrations decreased significantly during Ramadan compared with before fasting, but were still within the normal range. Salivary IgA concentrations also decreased significantly, whereas serum IgM levels did not change. Lymphocyte numbers increased significantly, but there was no correlation between Ig levels and lymphocyte count. Conclusion: Ramadan fasting did not result in severe immunological disturbances.