To investigate the frequency of allergic disorders in myasthenia gravis (MG) p atients and characterize the features of MG associated with allergic disorders. Frequencies of past and present common allergic disorders in 160 MG patients who visited the Department of Neurology, Kyushu University Hospital from April 2000 to July 2003 and in 81 neurological normal controls were studied. Among various allergic disorders, the frequency of allergic conjunctivitis (AC) was significa ntly higher in MG patients (39/160, 24.4%, Pcorr=0.011 2), especially with MG w ithout thymoma (36/123, 29.3%, Pcorr=0.001 6), in comparison to the controls (6 /81, 7.4%). MG patients with AC showed a significantly higher rate of seronegat ive MG (43.6%vs. 17.4%, P=0.008) and a higher tendency of ocular MG (43.6%vs. 28.1%, P=0.071). Moreover, MG with AC had significantly lower anti acetylchol ine receptor antibody titers (median 6.8 nmol/L vs. median 23.6 nmol/l, P=0.035 9) as well as a lower rate of coexisting thymoma (7.7%vs. 17.4%, P=0.016). The incidence of myasthenic crisis was also lower in MG with AC than without AC, ye t the difference was not significant (7.7%vs. 15.7%). There was a significant association of AC with MG especially for ocular or seronegative MG in cases with out thymoma. To investigate the frequency of allergic disorders in myasthenia gravis (MG) p atients and characterize the features of MG associated with allergic disorders. Frequencies of past and present common allergic disorders in 160 MG patients who visited the Department of Neurology, Kyushu University Hospital from April 2000 to July 2003 and in 81 neurological normal controls were studied. Among various allergic disorders, the frequency of allergic conjunctivitis (AC) was significantly higher in MG patients (39/160, 24.4%, Pcorr = 0.011 2) w ithout thymoma (36/123, 29.3%, Pcorr = 0.001 6), in comparison to the controls (6/81, 7.4%). MG patients with AC showed a significantly higher rate of seronegat ive MG %, P = 0.008) and a higher tendency of ocular MG (43.6% vs 28.1%, P = 0.071). In addition, MG with AC had significantly lower anti acetylcholinergic receptor titers (median 6.8 nmol / L vs. median 23.6 nmol / l, P = 0.035 9) as well as a lower rate of coexisting thy The incidence of myasthenic crisis was also lower in MG with AC than without AC, ye t the difference was not significant (7.7% vs. 15.7%). There was a significant association of AC with MG especially for ocular or seronegative MG in cases with out thymoma.