The total leucocytes, the basophils and the eosinophils were counted on 30 healthy and 62 sick children. The counting of the basophils and eosinophils was done simultaneously. Children with infectious hepatitis had during the acute stage a low number of basophils, when the liver function becomes normal again the number of basophils is rising, sometimes over the middle value of the healthy children. Also on children with scarlet fever and other infections the basophils and eosinophils had a rising tendency. Eosinophilia and basophilia were marked during the acute stage of the scarlet fever. There was a correlation between the numbers of the basophils and the eosinophils. Four hours and one day after tonsillectomy there was a marked decrease of eosinophils and basophils; five days after the operation the blood count became normal again. Also the total leucocytes were increased during these five days. If children with allergic diseases had an increased number of eosinophils also the basophils were increased.