Most　chlortetracycline　(CTC)　which　was　produced　in　fermentation　process　or　was　added　into　solution　diffused　into　mycelium　of　Streptomyces　aureofacins　while　seldom　did　into　other　microorganism　cells.　According　to　results　of　mycelium　disruption　of　S.　aureofaciens,　CTC　did　not　dissolve　in　cytoplasm　of　S.　aureofaciens　but　was　absorbed　by　intracellular　components.　Variation　of　pH　had　obvious　effects　on　CTC　absorption　of　S.　aureofaciens　cells,　and　more　than　95%　CTC　was　absorbed　by　mycelium　at　physiological　conditions　while　all　dissolved　in　solution　when　of　pH　value　is　lower　than　1.4.　From　body　solutions　into　cell,　CTC　transport　was　passive　diffusion.　Special　absorption　of　CTC　in　mycelium　of　S.　aureofaciens　may　be　one　important　factor　that　S.　aureofaciens　had　such　potent　resistance　to　CTC.