The feasibility of using an enhanced chemiluminescent immunoassay for screening water samples was adapted to a Dynatech Microlite camera luminometer and assessed to provide a semiquantitative assay based on a photographic record of the luminescent end-point. An enhanced chemiluminescent immunoassay of the herbicide chlortoluron was chosen in this instance as an example, although other pesticide compounds could equally well have been used provided that suitable antisera were available. This luminescent assay has shown considerable potential by providing a rapid, simple and portable means of monitoring multiple water samples for the presence of chlortoluron. The assay was able to identify samples containing the herbicide at or above the European limit for individual pesticides in drinking water [the EU Maximum Admissible Concentration (MAC)= 0.1 µg l^–1]. A 100% accuracy was obtained in the analysis of samples containing chlortoluron at concentrations above the range of 0.07–0.12 µg l^–1; however, for concentrations within this range the results were 65% accurate. Consequently, the method could greatly facilitate increased monitoring for the presence of chlortoluron in water supplies and in other areas of environmental analysis.