A soil isolate of Actinoplanes that produces the chemically unrelated new antibiotics teichomycins A₁ and A₂ has been proposed as a new species named Actinoplanes teichomyceticus nov. sp. (ATCC 31121). Studies of medium and fermentation conditions indicated that the highest antibiotic titers, cα 900 μ/ml, are obtained in a medium containing 1% (w/v) glucose, 1% cotton seed meal, 1% malt extract, and 0.4% yeast extract. Both teichomycin A₁ and teichomycin A₂ are highly active against gram-positive bacteria. Teichomycin A₁ shows some activity against gram-negative bacteria. Both antibiotics cured mice experimentally infected with sensitive bacteria and showed low acute toxicity. Of the two antibiotics teichomycin A₂ is the more active.