Laboratory batch sorption experiments were performed to study the effects of soil components and solution pH on methamidophos sorption in an alluvial soil profile. Soil samples were collected at depths (0-30cm (surface soil), 30-60cm, 60-90cm and 90-120cm). Our results show that methamidophos sorption increases with increasing solution pH, indicating that amino groups in methamidophos may be actively involved in the sorption processes. While methamidophos sorption in the surface soil is mainly controlled through partitioning into soil organic matter, soil minerals (e.g., clays, Al/Fe oxides) play an important role on the sorption of methamidophos in subsurface soils. The batch sorption. experiments also indicate that the mineral surfaces (e.g., clay or Al/Fe oxides) exhibit much greater sorption affinity for methamidophos at low methantidophos concentrations compared to the soil organic matter although the soil organic matter significantly increases the sorption capacity of soils.