Disclosed herein are peptide derivatives which inhibit the activities of human immunodeficiency virus (HIV) protease and renin. The peptide derivatives can be represented by general formula R.sup.1 --R.sup.2 --Y--R.sup.3 --R.sup.4 wherein R.sup.1 is a derived amino acid based on an O.sup.4 -(carboxymethyl)-tyrosyl residue, R.sup.2 and are amino acid or analogous amino acid residues (R.sup.3 may optionally be absent), Y is a non-peptide linking unit, e.g. statyl, and R.sup.4 is [--NR.sup.17 CHR.sup.18 --C(O)].sub.p --Z wherein R.sup.17 is hydrogen or lower alkyl, R.sup.18 is an amino acid or analogous amino acid side chain, p is zero or one and Z is a terminal group (e.g. hydroxy or amino), or R.sup.4 is --NR.sup.17 CR.sup.18 (R.sup.21)CH.sub.2 OH wherein R.sup.17 and R.sup.18 are as noted hereinabove and R.sup.21 is hydrogen, lower alkyl or hydroxy(lower)alkyl. The derivatives are useful as agents for combatting HIV infections and for treating renin-associated hypertension and congestive heart failure.