An investigation was carried out during 2000-01 to study the adsorptive behaviour of thiophanate-methyl on humic acid extracted from soil. Adsorptions of thiophanate-methyl by humic acid followed the Freundlich and Langmuir equations. Results showed that the adsorption capacity of humic acid depends both on nature and type of saturating cations present on humic acid surface. The order of adsorption of thiophanate-methyl by humic acid was humic acid> Ca- humic acid > Mg-humic acid in the soil studied.