I. An analogue of the herbicide atrazine was synthesised and conjugated to carrier proteins for rodent immunisation and monoclonal antibody screening. II. Monoclonal antibodies from hybridoma clone 1G18 specific for the herbicide atrazine were successfully isolated. A suitable ELISA system was optimised and the binding capability and cross reactivity of these antibodies was found to be broadly similar to two other anti-atrazine monoclonal antibodies that were acquired externally. III. The antibody variable region domains of hybridoma 4063-21-1 were cloned and fully sequenced. The variable region domains of hybridoma AM1B5.1 were cloned and partially sequenced. IV. The variable region domains of hybridoma 4063-21-1 were sub-cloned into an expression plasmid and fully functional antibody fragments, specific for the herbicide atrazine, were obtained from <I>E. coli</I> fermentations. The recombinant antibody bound antigen with a binding capability that was 10% that of the whole murine antibody. V. The best yields of anti-atrazine antibody fragment were obtained from fermentations in buffered medium when the fermentation broth pH was maintained above pH 6.0. The recombinant antibody was purified by immobilised metal chelate affinity chromatography and the purified antibody fragment was found to bind antigen 10% as well as the crude recombinant antibody.