A survey to estimate the potential demand for a bovine babesiosis and anaplasmosis vaccine was carried out by a postal questionnaire sent to 4407 veterinarians in the north and centre of Argentina. Twenty-three percent of the questionnaires (1047) were answered; 317 (7.2% of the total, 30% of those answered) pointed out the occurrence of the diseases and/or probable demand for the vaccine. The minimum and maximum demands were 407,892 and 982,300 doses for anaplasmosis, and 272,496 and 631,400 doses for babesiosis, respectively. The results presented from here onwards are based on the minimum demand. Sixty-eight and 48% of the anaplasmosis and babesiosis vaccine demand, respectively, came from veterinarians living in the Boophilus microplus-free area, while the remainder came from the tick-infested area, reflecting the fact that many farm owners from the tick-infested area seek professional assistance from veterinarians living in the tick-free area. Most of the demand for both vaccines was aimed at breeding cattle (77.2%), 14.5% at dairy cattle and the rest at studs (8.3%). Veterinarians living in the tick-infested area demanded vaccine for breeding cattle in a higher proportion than veterinarians from the tick-free area, whose demand was greater for dairy cattle. In the tick-free area, the demand for anaplasmosis vaccine was twice that for babesiosis vaccine, whereas in the tick-infested area the demand was equal. This agrees with the fact that the anaplasmosis-stricken area extends beyond the tick-infested region. Sixty percent of the respondents preferred a vaccine frozen in liquid nitrogen, whilst the rest preferred a refrigerated one, the first group accounted for 73% of the total demand. Fifty-six percent of the demand occurred between March and June with the peak in April, which reflects the main weaning date. The elasticity of the demand is discussed in relation to the probable benefits to be accrued by the farmers who make use of it. The annual mortality rates due to both babesiosis and anaplasmosis were estimated at 1.5 and 3.5% in the milk herds of Salta and Tucumán, respectively. In the beef herds of these two provinces, the mortality rate due to both diseases has been estimated at 3.5%. Using these figures and current prices, the systematic application of the vaccine in calves would render a benefit-cost ratio between 4.6 and 9.0, which would warrant its use in the herds of the areas at risk, i.e. in enzootic instability.