A white Thermus sp. strain, NCIMB 11245, showed high levels of anteiso C(17:0), anteiso C(17:1), normal C(16:1), and iso C(16:0) with low levels of iso C(15:0) + iso C(17:0) in comparison to yellow-pigmented strains. The fatty acid composition may be associated with precursor metabolism or the absence of carotene pigmentation.