Resting cells of Kluyveromyces marxianus were used in the bioreduction of ethyl 4, 4, 4- trifluoro-3-oxobutanoate and ethyl 4, 4, 4-trichloro-3-oxobutanoate with 81% and 4% yields and 29% and 73% enantiomeric excess, respectively. The differences observed were attributed to the tri-halide structures.