The Authors have carried out some experiences on four tests for the detection of anti O streptolysin, determining in 210 samples of sera: 1. the antistreptolysin titer according to Rantz and Randall; 2. the antistreptolysin titer according to the latex reaction; 3. five different antistreptococcal antibodies (ASO, ASK, ASHA, ADN-aseB, NAD-ase) with a rapid multi-purpose test for a simultaneous detection; 4. the antistreptolysin titer according to Aso Quantum method. The results obtained on the 210 samples of sera were compared. The relationship between the four methods were examined.