Neutralization test and the method of indirect immunofluorescence were used to study the titre of specific antibodies in 32 paired serum samples taken from subjects naturally infected by varying RV serotypes [1A, 1B, 9, 12, 15, 16, 19, 23, 26, 29, 30, 31, 41, 47]. The IF method was positive in all the examined sera, the increase in the titre of rhinovirus-specific antibodies was mostly low and in 10 cases was the titre in both serum samples identical. The neutralization test turned out to be less sensitive in detecting specific antibodies. In serum samples from 13 examined subjects it failed to detect antibody presence in either of the two serum samples, in 15 subjects was recorded an increase in the titre of antibodies, but in some of them was only small, and the identical antibody titre in both serum samples was detected in 4 subjects.