Polycyclic aromatic hydrocarbons (PAHs) represent health and environmental concerns. The present study was designed to develop a highly sensitive and reliable immunochemically-based non-instrumental field assay to monitor the presence of benzo[a]pyrene (BAP) in aqueous samples at the ppt-level using visible test evaluation. The corresponding gel-based immunoassay was set up to combine preconcentration and detection of the target analyte using anti-PAH antibodies and horseradish-BAP tracer conjugate in one single cartridge. Water sample preparation, such as extraction, centrifugation, or filtering was found to be unnecessary. No interference by higher water-soluble PAHs at 4000-fold excess compared to BAP was observed. The assay was configured as a qualitative test (positive/negative) at the cut-off level of 5 ng L(-1), however, this level can be adapted to the required analyte concentration by rather simple adjustment of the anti-PAH antibody concentration of the test zone. Test validation was performed with real samples such as surface water, melted snow, and tap water using high performance liquid chromatography with fluorescent detection (HPLC-FLD) with solid phase extraction for validation.