This study examines factors affecting the spatial variability of soil infiltration in cultivated fields in a Mediterranean environment. The study area is a wine growing catchment located near the town of Roujan (Hérault) in the South of France. The steady state infiltration rate was measured in 1 m² plots in a sample of eight untilled vineyards, using a rainfall simulator. Five measurements were made in each field in order to assess the between- and within-field variability of infiltration. The factors affecting variability of soil infiltration (field effect, slope, soil type, structure of the first few centimetres of the soil, roughness, texture, grass cover and surface water content) were analyzed. A simple classification of the topsoil structures is proposed. Analyses of variance were carried out as a first step, to test the effect of these factors on infiltration in all measurement plots. An attempt was made to simplify these results by grouping together fields with homogeneous characteristics. The results show that 40% of the total variance of observed infiltration rates can be explained either by differences between fields or by differences in local topsoil structure. The latter two criteria are easily observable and can therefore be used in practice for stratifying the spatial variability of infiltration rates.