Mephenamic acid is characterized by low solubility, which affects its dissolution rate and bioavailability. The objective of this study was to develop fast-release microspheres of ammonium salt of the drug (AMM) by emulsion congealing.The effect of polymer, drug to polymer ratio, surfactant, type and volume of oil phase, stirring rate, microsphere size, encapsulation efficiency and stability of the microspheres were investigated. The results pointed out a good yield (69-98%) and encapsulation efficiency (71-100%). Optimum conditions include moderate molecular weight PEG, inclusion of Tween 20 and/or Span 80, high ratio of PEG (1 : 4, drug : PEG), use of mineral oil and high stirring rate (2000 rpm). Dissolution efficiency ranged between 57% and 90%. Effect of ageing on drug content and release revealed that the microspheres prepared remained stable throughout 1 year of storage. The described method was simple, efficient and resulted in stable microspheres with enhanced drug release.