Sodium, potassium, chloride, glucose and total protein were determined in samples of scala vestibuli perilymph, scala tympani perilymph, CSF, cochlear endolymph and utricular endolymph from normal cats. Small but significant differences were evident in the concentrations of sodium and potassium between the scala vestibuli and scala tympani perilymph. It was also apparent that each compartment of endolymph has different values for sodium and potassium concentrations. Compared with the endolymph, the perilymph was found to contain a higher concentration of glucose and total protein. These findings are discussed from the view point of biological significance.