The absolute configuration of lyngbyatoxin A (teleocidin A-1) and teleocidin A-2, potent tumor promoters on mouse skin, has been determined by chemical degradation including ozonolysis. The results showed uneqivocally the C-14 absolute configurations of lyngbyatoxin A (teleocidin A-1) and teleocidin A-2 as R and S, respectively. The absolute configurations at C-9 and C-12 in lyngbyatoxin A (teleocidin A-1) were elucidated as S, S in a previous paper, and teleocidin A-2 has the same configuration on the nine-member lactam as evidenced by the same CD spectra.