Two selective culture media are described. The first, tellurite streptococcus medium, has the following composition: water, 1,000 ml.; Bacto tryptose, 20 g.; Bacto agar, 15 g.; sucrose, 50 g.; glucose, 1 g.; and K2HPO4, anhydrous, Merck reagent, 4 g. Adjust to pH 7 and add 0.8 ml. of 0.1% crystal violet (C.C.), based on the dye content of the sample, not on its crude wt., and 7.5 ml. of 1.0% trypan blue. Sterilize as usual. When ready to pour, add 0.4 ml. of a stock soln. of 5% unheated K tellurite which is manipulated with aseptic precautions. Incubate the cultures exactly 24 hrs. This gives excellent recovery of streptococci, even from minute inocula, with good differentiation between Streptococcus salivarius, S. mitis, and enterococci. Organisms other than streptococci rarely grow on the medium.[long dash]The 2d medium is a blood-agar composed as follows: water, 1,000 ml.; Bacto tryptose, 20 g.; glucose, 1 g.; sucrose, 5 g.; NaCl, 5 g.; agar, 15 g.; "S.T 37," 0.5 ml.; Na azide, 0.06 g. Adjust to pH 6.8 and add 1 ml. of 0.10% crystal violet (C.C.) based on the dye content of the sample and not on its crude wt. Sterilize as usual. When ready to pour add the desired amt. of blood. Incubate the cultures 26 to 28 hrs. (not "overnight"). This gives only fair inhibition of coliforms but is valuable in detecting S. mitis.