Aerobic laboratory soil degradation studies and field soil dissipation trials demonstrated that penconazole is degraded under non-sterile incubation conditions to several metabolites and non-extractable residues and progressively but slowly mineralised to carbon dioxide. Penconazole was essentially stable under anaerobic conditions and in aerobic sterile soil and only very slowly degraded via photolysis on a soil surface. The principle mechanism of penconazole degradation in soil is therefore via aerobic soil microorganisms. Degradation is thought to proceed principally via oxidation of the aliphatic side chain yielding CGA 179944, i.e. 2-(2,4-dichloro-phenyl)-3-1,2,4-triazol-1-yl-propionic acid. Bridge cleavage leads either directly or via the intermediate CGA 142856 (1,2,4-triazol-1-yl-acetic acid) to CGA 71019 (1H-1,2,4-triazole). Finally, probably via formation of further minor polar degradates, the last metabolic steps generate carbon dioxide and non-extractable (bound) residues. CGA 71019 is unstable in aerobic soil and no significant extractable metabolites are observed; its principal fate is believed to lead to the high formation of bound residues and some carbon dioxide. Under anaerobic conditions primary degradation of the penconazole metabolite CGA 71019 is low. Dissipation under anaerobic conditions is characterised by a continuous formation of CGA 142856, a moderate plateau of nonextractable residues and a negligible formation of CO2. Most metabolites found in aerobic penconazole degradation studies were minor metabolites accounting for less than 5 % of the applied radioactivity (AR). Identification was not generally possible due to the low amounts formed and transient occurrence. CGA 71019 (1H-1,2,4-triazole) was the most prominent metabolite found at peak levels of 20 to 40 % AR. The metabolite CGA 179944 is an intermediate metabolite with a slightly delayed degradation (DT50 values of 4.5 to 15.5 days) and a maximum peak of 7 % AR under aerobic conditions. In one early study where non-standard conditions were used (e.g. dry soils, low temperatures) and the incubation period was extended up to 1 year, CGA 179944 reached up to 19 % AR. However, these artificial laboratory conditions are known to reduce microbial activity in the soil and are thought unlikely to represent behaviour under normal use conditions. Only two metabolites exceeded 10 % AR: CGA 179944 with a maximum of 18.9 % AR and CGA 71019 with a maximum of 38.6 % AR. Under standard aerobic conditions concentrations decreased towards the end of the studies. No degradation products derived from the phenyl-moiety of penconazole were detected indicating a rapid dissipation by a rather moderate mineralisation in combination with the formation of significant amounts of non-extractable residues. The mineralisation of penconazole to carbon dioxide in most studies proceeded continuously but slowly throughout the aerobic incubation periods since dissipation of penconazol from soil is mainly accompanied by the formation of significant amounts of metabolites and nonextractable residues. Based on a standard incubation time of 100 days mineralisation rate for penconazole has to be classified as being negligible with CO2 formation below 10 % in most studies. Within an incubation time of 6 to 12 months penconazole is mineralised in laboratory studies up to ca. 38 % AR, depending on soil type, soil moisture, temperature and application rate. Data from comparable experiments with both radiolabels indicated that degradation to carbon dioxide was about one order of magnitude more efficient in the phenyl-ring than in the triazole-ring. A greater efficiency in mineralisation could be also demonstrated for lower application rates though the difference was only about a factor of two. Dissipation of penconazole in most studies is accompanied by the formation of a significant proportion of non-extractable residues . The formation of non-extractable residues reaches a maximum of between 20 and 40 % AR over a period of 6 to 12 months. Organic matter fractionation demonstrated that about two thirds of the non-extractable residues were associated with the humic and fulvic acid fractions, whilst one third was still bound to the insoluble humin fraction even after excessive extraction. Therefore, organic matter fractionation demonstrated the strong incorporation of a significant proportion of penconazole equivalents into the soil matrix.