Abstract
The mean spherical approximation (MSA) is found inadequate in the presence of attraction between particles which is strong and of short range compared with the hard core diameter. This is a situation prevalent in applications of liquid state theory to micellar solutions and microemulsions. A generalized MSA is also studied in which conditions of thermodynamic consistency are implemented. The critical point is determined as function of the range of the attractive forces. We also discuss how the inadequacy of MSA affects the effective pair interaction deduced from experimental data for the structure factor.