Abstract: The activity of erythrocyte acetylcholinesterase （RBCAchE） was measured in 27 children with breathholding spells and in 22 normal controls.The mean RBGAchE activety is significantly lower in clildren with breathholding spells,compared with that in normal controls and a highly significant statistical negative correlation between the frequency of spells and the RBCAchE activity is demonstrated.18 cases with frequent attacks （＞1/month） receiving iorn therapy for more than one month were followed up for 3—12 months.It was found that 11 cases were free of spells within 2 weeks aftet iorn therapy,the episodes were reduced by over 75% in 4 cases and less than 75% in 3 cases.In cases with episodes stopped the RBCAchE activity returned to normal, while in cases with episodes not stopped the RBCAchE activity remained low.The results of this study suggested that the dynamic and sequential observations of RBCAchE activity may be useful to predict the prognosis and the breathholding spell is not the response of children to stress situation.