The magnetic behavior of N,N'-ethylenebis(salicylideniminato)cobalt(II) (Co(II)Salen, 1) has been reinvestigated and reveals spin-crossover behavior above 295 K. It has a singlet ground state and a triplet excited state at 30 K (21 cm(-1); 60 cal/mol) above the ground state, and at a higher temperature spin crossover to the quartet, a second excited state occurs.