Abstract: Pyrogen testing is one of the most difficult problems encountered in quality control of radiopharmaceuticals. The increased use of short-life radiopharmaceuticals presents formidable problems in pyrogen testing by the official method because of the rapier physical decay of most radionuclides, the large volume of required test solution, the radiation exposure and waste-disposing problems.The Limulus test is a rapid, sensitive and simple method for detection of bacterial endotoxin (pyrogen).We prepared amebocytes lysate from Horseshoe crab of China i. e. Tachypleus tridentatus. Its sensitivity was found to be 1～10 ng/ml for E. coli O₁₁₁B₄ endotoxin. An improved micromethod of slide test was used as a modified Limulus test in our laboratory. In testing 50 batches of radiopharmaceuticals for pyrogen by rabbit and Limulus methods, the results of 38 batches were in agreement with each other.Preliminary results indicate that the Limulus test is a rapid, sensitive and simple method for detection of pyrogen in radiopharmaceuticals.