From December 1997 to March 1998, a sample survey was conducted in Belgium to estimate the national bovine paratuberculosis (PTB) herd and animal seroprevalence. This survey aimed to provide an unbiased estimate of the PTB seroprevalence, as the sampling units were randomly selected using the co-ordinates for the cattle herds registered in SANITEL-Cattle, the central computerised database for the identification and registration of cattle in Belgium. A stratified sample design was followed. The total number of herds to be sampled was set at 1 % of the total number of Belgian cattle herds, and the number of herds to be sampled per province was determined by proportional allocation. In the selected cattle herds, all adult cattle of 2 years or older were blood sampled. A herd was defined to be PTB-seropositive if at least one PTB-seropositive adult bovine was present. The serum samples were tested for antibodies to PTB, using a commercially available Absorbed ELISA test-kit (HerdChek, IDEXX, France). Seventy seven of the 442 herds had at least 1 PTB-seropositive adult cow. Consequently, the PTB herd seroprevalence was 17.42 %. The individual animal seroprevalence was 1.18 %; 143 of the 12.077 adult cattle were seropositive to PTB. Detailed analysis of the seroprevalence for different herd and management characteristics are in progress.