Fourteen patients with radiculomyelitis following acute haemorrhagic conjunctivitis (AHC) were seen in Bangkok during October to December 1974. Most patients developed weakness of extremities 2 weeks after AHC. Prodromal symptoms consisted of fever and malaise for a few days, followed by the acute onset of root pain in the legs and flaccid paralysis. Knee and ankle reflexes were absent or diminished. Cerebrospinal fluid examination revealed lymphocytosis and an increase in protein. Electromyographic findings were consistent with anterior horn cell or motor root lesions. Ten of the 12 cases in which virological studies were performed showed definite serological evidence of AHC virus infection. Six patients received corticosteroid treatment but apart from relief of pain no significant improvement was seen. Motor weakness in 10 patients was less at the end of 2 months, but in 4 it remained unchanged. The occurrence of disabling neurological sequelae calls for effective public health control of AHC outbreak.