The earthquake of magnitude 7.3 that occurred near the town of Haicheng in northeast China on 4 February, 1975 was the first major earthquake anywhere in the world known to have been predicted with enough certainty for people to have been warned, and measures taken for civil protection. These steps were successful in keeping the number of casualties small. This paper describes a visit to the affected area seven and a half months after the earthquake, and discussions with Chinese scientists about their successful prediction methods. The prediction resulted from the synthesis of many types of investigation, but the main methods used for long-, mid-, and short- term prediction appear to have been based on studies of seismicity, deformation, and foreshocks respectively.