Objective To investigate the value of ice test in the diagnosis of ptosis of myasthenia gravis(MG). Methods A total of 32 patients with myasthenic ptosis and 33 with nonmyasthenic ptosis underwent ice and rest test which were performed alternately twice within 1 day on each patient. Besides, neostigmine test was performed on the patients with myasthenic ptosis after ice and rest test . Two observers who didnrsquo;t know the clinical diagnosis were asked to evaluate the improvement of eyelid elevation by measuring the width between the midpoints of upper and lower eyelid with a 20mm steel rule (precision of 0.5 mm). The average of margin of palpebral fissure width after double ice or rest tests subtrac ted from the one before the tests in one patient was the standard of the improve ment of eyelid elevation. Results Ice and rest test improved myasthenic ptosis but not nonmyasthenic ptosis with the specificity of 100% in both of the tests. In addition, ice test improved myasthenic ptosis more effectively with a higher sensitivity of 78%, and it could also improve the palpebral fissure width in pa i tents with complete myasthenic ptosis apparently. Compared with the neostigmine test, ice test had lower sensitivity, cost shorter time, didnt need injection which avoided the discomfort, and had no side effects. Conclusion Ice test is a simple and safe means with high sensitivity and specificity to diagnose myasthenic ptosis, which is valuable in clinical application. (Chin J Ocul Fundus Dis, 2006,22:382-384）