A simple treatment for surface tension in immiscible fluids is proposed for macro-scale particle methods such as smoothed particle hydrodynamics (SPH) and macro-scale pseudo-particle modeling (MaPPM). By introducing a repulsion between the neighboring particles of different fluids, surface tension arises automatically, while simple equations of state are still possible for each phase. This treatment is validated by comparative simulations on the deformation of a square liquid drop in suspension using the volume of fluid (VOF) method. The relationship between surface tension and the repulsion intensity parameter in our model is obtained by the sessile drop method. (C) 2007 Elsevier B.V. All rights reserved.