Leptosols (LP) constitute the soils group with the largest extent worldwide (12%), in México (24%) and in Yucatán (80%). However, LP have been so far scarcely documented and studied. In Yucatán, Maya people have developed a soil classification adapted to small karstic areas on the basis of their century-long experience of cultivating such areas (Dunning, 1992; Bautista et al., 2000; 2001; 2003ab; 2004; 2005ab; Duch, 2005). Local people have also a deep knowledge of native plants (Flores, 1994; Flores y Bautista, 2005). The Mayan soil knowledge can be used to improve technical soil classifications in karstic areas, especially concerning the Leptosol group. The purpose of this paper is to compare the Mayan soil classification (MSC) with the WRB classification. The study area is located in the lowlands of the State of Yucatán in México. In interviews, local peasants were asked to identify and name the soil types they knew, describe their properties and show how they recognize them. Soils were described, sampled and classified in the field using the WRB system (WRB, 2002). In the period 2000-2003, three soil-geoform surveys were conducted with the help of bilingual (Maya-Spanish) peasants (Uicab, 2002; Bautista et al., 2004; 2005b). A soil data base was constructed with 300 profiles representing Leptosols (LP), Cambisols (CM), Calcisols (CL), Luvisols (LV), Lixisols (LX), Vertisols (VR), Regosols (RG) and Arenosols (AR). The Mayan peasants identified soil classes based on relief, soil color, texture, drainage, stoniness, rockiness, gravel content and depth. Soil classes in the MSC were: (a) K'ankab, red soils, 10-100 cm deep or deeper (CM, LV); (b) Hay lu'um, soils with the same characteristics as K'ankab but less than 10 cm deep and containing more fine earth than the Chaltún soil class (LPli); (c) Chaltún, soils that can be red, reddish brown or black, with large amounts of coarse fragments and frequently interrupted by rock outcrops of laminar limestone (LPli); (d) Aak'alche, grey soils, clayey, poorly drained, 100 cm deep or deeper (VR); (e) Ekluúm, black or brown soils on higher relief portions, good for agriculture (LV); (f) Chak lu'um, 10-60 cm deep soils, redder than K'ankab (CMlen, CMlep); (g) Yaax hom, yellow soils, 100 cm deep or deeper, without stones, hard when dry, with good water retention (LX); (h) Box lu'um, black soils, typical of higher relief portions, with stones of 5-10 cm diameter (LPli, LPhsk, CL); (i) Ch'och'ol, also black soils but with less fine earth than the Box lu'um soils, with frequent rock outcrops and abundant coarse fragments of 5 cm diameter or more (LPhsk); (j) Tsek'el, black soils, with very little fine earth though more than in the Chaltún class and with bedrock outcrops in the form of promontories (LPli); (k) Chich lu'um, soils with abundant gravel content (LP, CL); and (l) Pus lu'um, shallow soils with soft black earth and good drainage (LPrz). The MSC classification established a clear difference between Hay lu'um and Chaltún soils within the Lithic Leptosols. The WRB, in contrast, differentiated between Leptosols (<25 cm) and Cambisols (>25 cm), a distinction that is not taken into account in the MSC. Although 25 cm depth may be an arbitrary threshold, it is a useful indicator of the soil volume available for root development. Similarly, the K'ankab soil class was divided into two subclasses based on depth, resulting in a shallow (10-25 cm) K'ankab and a deep (>25 cm) K'ankab. Stoniness used in the MSC has agricultural and pedogenetic implications in karstic enviroment. The soil development sequence on lower slopes includes the following WRB members: LPli–CMlep–CMskn–CMlen–LVro. On upper slopes, the soil development sequence includes the following WRB members: LPli–LPrzsk–CLlepsk–CLptp; also the sequence LPli–LPrzsk–LPhskca is likely to occur. Soil catenas as related to geomorphic units are LP-LP on subhorizontal plains; LP-LCM or CL-CM on undulating plains; and LP or CL-LV on plains with hills. Random soil variability is controlled by the rock type in each geomorphic unit. The MSC and WRB classifications are complementary. It is recommended to use both systems for a maximum level of detail, as together they offer a good vision of the soil resource in the study area.