Treponema denticola and Treponema vincentii were found to require albumin, oleic acid, and thiamine pyrophosphate (TPP) for growth. Previous studies indicated that commercial human alpha globulin, which is 50% albumin, was the only serum fraction that supported growth of these two oral treponemes. The alpha-globulin proteins were separated from the contaminating albumin with Affi-Gel Blue affinity chromatography. Both the albumin fraction and one of the alpha-globulin fractions were required for growth of T. denticola. Oleic acid was supplied by the alpha-globulin fraction and the albumin functioned as a chelator to maintain a low level of free fatty acid in the medium. Purified serum albumin (bovine or human) could substitute for the alpha-globulin fraction that contained albumin. Optimal growth of T. denticola and T. vincentii was in a medium supplemented with 0.4% (w/v) delipified albumin, 0.08 mg/mL of sodium oleate, and 25 µg/mL of TPP. Serum albumin tightly bound TPP (0.5 µg of TPP per milligram of albumin). Optimal growth of T. denticola was only in an albumin–oleate supplemented medium with sufficient TPP to saturate the albumin binding sites and provide excess free TPP. Albumin bound long-chain fatty acids and thus detoxified the medium. Neither starch- nor charcoal-treated Tween 80 (polysorbitan monooleate) replaced albumin for optimal growth. Short-chain fatty acids supported only limited growth of T. denticola when added to a medium with TPP or to a medium that contained 0.4% delipified albumin and TPP.