Sulfadiazine is a widely used antibiotic pharmaceutical in intensive livestock production. 40 -90 % of the applied pharmaceutical are excreted, mainly as active compound after administration. Antibiotics such as sulfadiazine reach agricultural soils directly through grazing livestock or indirectly through the spreading of manure or sewage sludge on the field. Knowledge about the fate of antibiotics in soil is crucial for assessing the environmental risk of those compounds including possible transport to groundwater. Transport of ¹⁴C-labelled sulfadiazine was investigated in disturbed soil columns at a constant flow rate near saturation. Sulfadiazine was applied in different concentrations (5.7 vs. 0.57 mg L^-1) for either a short or a long pulse duration (7 vs. 68 h). Breakthrough curves of sulfadiazine and the non-reactive tracer Cl^- were measured during 500 h. At the end of each experiment the soil concentration profile was determined. The breakthrough curves were characterised by an early arrival of sulfadiazine and a pronounced tailing. The peak maxima arrived at approximately the same time for all experimental conditions, but the maximum relative concentrations differed as well as the eluted mass fraction. Whereas for the experiments with the longer pulse duration the highest concentrations in the soil profile were found near the surface, the concentration distribution with depth was more constant for the short pulse experiment. To identify relevant sorption processes, breakthrough curves of sulfadiazine were fitted with a convective-dispersive transport model considering different sorption concepts. One, two and three sites sorption models were tested and their assumptions and limitations are discussed. Breakthrough curves can be fitted best, with the assumption of instantaneous, kinetic reversible and irreversible sorption sites, but the simulated soil concentration profiles did not match the observations.