Supravital staining of granulocyte, lymphocyte and reticulocyte was carried out with a series of dyes including both acidie and basic ones. On each dye the affinity to cells was observed in those media which pH were changed serially from 1 to 13 using Mcllvaine's or Sorensen’s buffer solution. On the other hand the increasing or decreasing effect of hydrogen ion concentration of media on the charges of dyes was observed electrophoretically. In general, strongly charged dyes, both positive and negative, failed to invade into cells in the whole range of pH, while the Weakly charged dyes showed a positive stain in a certain region of pH, i. e. the acidic dyes in the acidic media and hasic dyes in the basic media, showing the accelerated permeability of dyes to cells in their fairly discharged states. However, some dyes proved to be inpermeable even in their weakly charged states. This inpermeability was attributed to the large molecnlar weight of the dyes or to the sparing solubility to water, alcohol, ether and ether-alcohol.