The tentative identification of two neurophysins in human pineal glands is reported. The presence of these carrier-proteins for neurohormones was demonstrated by two different radioimmunossays: one highly specific for human pituitary estrogen-stimulated neurophysin (h-ESN) and the second for pituitary bovine neurophysin II (b-NII). These neurophysins accounted for about 0.425% of the total soluble pineal proteins. They were eluted from Sephadex G-75 column with the same elution volume as 125I labeled h-ESN. Their dilution curves were parallel to the standard curves of h-ESN and b-NII, respectively. Electrophoresis on polyacrylamide gel separated two distinct neurophysins. The less anodic neurophysin corresponding to b-NII and the faster moving one to h-ESN. The two proteins were named human pineal neurophysins I and II (h-PNI and h-PNII) in the order of their electrophoretic mobility. Purification of pineal neurophysins by isoelectric focusing resulted also in the separation of two neurophysins: one, recognized by antibody against h-ESN with an isoelectric point (pI) of 4.6, the other recognized by antibody against b-NII with a pI of 4.9. The presence of neurohormone(s), assessed by radioimmunoassay for [8-arginine] vasopressin, was also demonstrated. Under optimal conditions for the association the neurophysin and the neurohormone were eluted from Sephadex columns as a complex. This complex could be dissociated in 0.1N formic acid and the neurophysin and the neurohormone separated on Sephadex G-75.