The effect of pinealectomy (PX) and sham-pinealectomy (SPX) on the calculated concentration of NaCl in the total volume of fluid drunk per day ([NaCl]i) in female rats offered a free choice between water and 3% NaCl solution was measured. In normal rats the [NaCl]i increases after attainment of sexual maturity. The increase can be accelerated by neonatal PX. Neonatal ‘masculinization’ of female rats by testosterone propionate (TP2) removes the increase of [NaCl]i in adult females and suppresses the acceleration due to PX. Neonatal SPX interferes with this decreasing effect of TP2 in adult female rats. The role of the pineal gland in the regulation of water and salt intake is discussed in relation to sex differences, sexual maturation and neonatal str