AbstractMeasurements by gas‐liquid and high performance liquid chromatography confirmed that 3,5‐dichloroaniline was an important degradation product of iprodione in soil, and demonstrated that it could be extracted in relatively high concentrations when iprodione degradation was rapid. A colorimetric test based on the production of a diazo colour complex was shown to differentiate between amounts of the aniline in the range from 2 to 15 μg. The test was used to examine 3,5‐dichloroaniline production from iprodione incubated at 50 mg kg−1 in 33 soils with previously‐measured iprodione degrading properties. A positive colour reaction in acetone extracts made after 3 days was obtained with those soils in which the time to 90% degradation of iprodione was less than 6 days. A positive reaction after 7 days was obtained when this time was less than 14 days, and a positive reaction after 10 days was associated with a time to 90% degradation of less than 22 days. Preliminary studies with vinclozolin indicated that the test could also be used to identify soils which rapidly degrade this fungicide.