Occurrence as well as the subcellular activities of trypsin and chymotrypsin have been demonstrated in the developing human placenta. Activities of both these proteases are discernible in all the subfractions of the placenta as early as in the 6th week of gestation. Maximum activities are found to be associated with the microsomal fraction (105,000 g pellet) of early and mid placenta, however, at late gestation the soluble supernatant fraction (105,000 g supernatant) exhibits maximum localisation of these enzymes. Tryptic and chymotryptic activities increases significantly with the advancement of pregnancy at least up to 22 weeks and decreases in term placenta in all the particulate fractions, though higher than that found in early gestation. Soluble supernatant fraction of term placenta shows enhanced activities of both these enzymes which possibly indicate an increased solubilisation of the membranes which, in turn, may be significant in the maturation processes of the placental tissue.