The object of the study was to evaluate the effect of an experimental vaccine against Mycoplasma bovis infections on selected humoral immune parameters in the calves. The study was carried out on twelve calves divided into two equal groups: experimental and control. The experimental calves were subcutaneously injected with experimental vaccine composed of suspension of the M. bovis field strain of with saponin and lysozyme. The control group was administered with PBS by the same route. Blood samples for laboratory analyses were collected from all the animals directly prior to the proper experiment (zero test), then at daily intervals up to the 7th day of observation and next at weekly ones up to the 12th week after the vaccination. Serum samples were examined for total bovine immunoglobulins (Ig) and their individual classes (IgG, A i M) using suitable ELISA kits. In response to the vaccine the total serum concentration of Ig was at first lower than in the control animals up to the 56th day of observation, then it increased up to the end of the study. A distinct stimulation of the IgG synthesis was observed in the experimental animals throughout the study with the exception of the 42nd and 77th days when it was slightly decreased. On the other hand the IgA concentration was considerably lower in the experimental calves when compared to the control up to the 7th day of observation, whereas it was visibly increased at day 63rd and 70th after the vaccination. In response to the vaccination the IgM concentration had comparable values to the control throughout the study with the exception of the 4th and 56th days when they were considerably higher, whereas the IgM decrease was observed only at the 21st day after the vaccination. The experimental vaccine composed of the field strain of M. bovis with saponin and lysozyme caused significant activation of selected indices of humoral immunity in the affected animals.