SYNOPSIS. Blepharisma intermedium was cultured axenically. The organisms were freed of contaminating microorganisms by serial washing in a sterile salt solution. The major nutrients in the various media were: Freshly killed or lyophilized and autoclaved bacteria (Pseudomonas ovalis), yeast extract prepared from Fleischmann's baking yeast or Fleischmann's yeast autolysate, lettuce infusion or stigmasterol, 6 B‐vitamins, and phosphate buffer at 2 times 10−3 M. The cultures were kept in the dark at 25 C. Altho the 1st division after transfer into fresh media was delayed, B. intermedium divided in approximately 32 hours thereafter in most of these media.