4-Dimethylaminomethyl-1-(3-hydroxyphenyl)-1-nonen 3-one hydrochloride (II) was shown to stimulate respiration in ratlivermitochondria at levels of 2.5 mumoles or less; but at levels higher than 5.0 mumoles, respiration was inhibited when succinate and 3-hydroxybutyrate were the substrates. Compound II caused inhibition of respiration in the presence of glutamate over the dose range studied. The stimulating