Extraction of microamounts of strontium by a nitrobenzene solution of hydrogen dicarbollylcobaltate (H+B-) in the presence of dicyclohexyl-18-crown-6 (DCH18C6, L) has been investigated. The equilibrium data have been explained assuming that the complexes HL+, HL, SrL2+and SrL are extracted into the organic phase. The values of extraction and stability constants of the species in nitrobenzene saturated with water have been determined.