A more economical method has been developed for conversion of phosphogypsum to phosphoplaster using a refinement and calcination method. The refinement of phosphogypsum was carried out by washing the phosphogypsum with 0.4% milk of lime at 20 degrees C for 5 min. Then the refined phosphogypsum was calcined at 150 degrees C for 30 min, as in the conditions outlined by DTA-TG. The strengths and setting times of phosphoplasters were compared with those of commercial plaster. Some set retarding agents such as sodium citrate were also used to retard the hydration of phosphoplaster. It was concluded that the refined phosphoplaster can be used instead of commercial plaster.