The population structure and the establishment microsites of the Agave offoyana populations in Lomas de Galindo and the Pan de Matanzas were studied. These occur in a xeromorphic thorny thicket on serpentine and in a mesophytic semi-deciduous forest on calcium carbonate rocks, respectively. Five levels of rosette diameter for the age structure were considered and the density and spatial distribution of the individuals were evaluated. Microsites were compared with and without juveniles in terms of number of juveniles, number of leaves and length of major leaf, distance from other herbs, trees, shrubs, and other Agave species (larger than 1m in diameter) and Leptocereus scopulophilus, plus density, percentage of rockiness, bare soil, litter layer and lighting. The relationship between these variables with the presence or absence of juveniles in the microsites was evaluated, as well as their estimated probability. In Lomas de Galindo, middle class individuals predominate; while in the Pan de Matanzas those over 1m, with little representation of intermediate categories. In both populations there is an aggregate pattern of spatial arrangement and similar densities. The juveniles were found on the ground in Lomas de Galindo and in the hollows of the rocks in the Pan de Matanzas, so the availability of microsites seems not to limit recruitment. Germination and establishment is capable of occurring anywhere, independent of nurse plants or any other associated factor.