Succinoylamino hydroxyethylamino sulfonyl urea derivatives of the formula: ##STR00001## wherein R.sup.1 R.sup.6, R.sup.7, R.sup.7', R.sup.8, R.sup.30 R.sup.34, X', Y, Y', t, x, and n are as defined herein, are effective as retroviral protease inhibitors, and in particular as inhibitors of HIV protease.