The utilization of a coagglutination technique for the identification of a human source for feeding mosquitoes is described. The dilution of ingested blood samples in filter paper was performed in 2 mL of a sodium chloride solution at 0.85%. It was used a suspension of sensibilized Staphylococcus aureus with rabbit's serum, human plasmatic anti-proteins, and human anti-IgG rabbit's serum discriminated well between human and non human blood. No agglutination was observed with the negative control. This technique proved to be sensitive to identify 100% of the human blood samples taken to the paper 24 hours after the mosquitoes completed their feeding at a temperature of 26 to 28 degrees C. Among mosquitoes fed and collected in the fields the test had a satisfactory result. Therefore, it may be used in routine work in the fields. The results showed the sensitivity and specificity of this method for identifying human blood ingested by mosquitoes.