The seasonal and spatial variability of soil erosion under contrasting slope aspects in southeastern Spain was studied by performing and interpreting 84 rainfall simulation experiments conducted at an intensity of 55 mm h⁻¹ during 1 h. The vegetated soils on the north-facing slope and the upper afforested parts had negligible sediment yield, runoff and erosion, while the bare soils on the south-facing slope had very high runoff rates. Runoff sediment concentration decreased over time during simulated rainfall events on the vegetated areas while it increased on the bare ones. Solute release decreased over time on both surface types. Seasonally, runoff sediment concentration was highest in autumn, decreasing in winter and spring, due to the exhaustion of erodible soil and the vegetation growth. Sediment concentrations increased slightly in summer when runoff and erosion rates where very low. Increasing seasonal variability corresponded with increasing runoff and soil loss rates. Key words: Runoff, soil loss, Mediterranean, erodibility