The present invention provides methods for treating Pneumocystis carinii pneumonia and Giardia lamblia in a subject in need of such treatment. The methods comprises administering to the subject a compound of Formula I: ##STR1## wherein: X and Y are located in the para or meta positions and are selected from the group consisting of H, loweralkyl, loweralkoxy, and ##STR2## wherein: each R.sub.1 is independently selected from the group consisting of H, loweralkyl, alkoxyalkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, aryl, or alkylaryl or two R.sub.1 groups together represent C.sub.2 -C.sub.10 alkyl, hydroxyalkyl, or alkylene, or two R.sub.1 groups together represent ##STR3## wherein m is from 1-3 and R.sub.7 is H or --CONHCR.sub.8 NR.sub.9 R.sub.10, wherein R.sub.8 is loweralkyl, and R.sub.9 and R.sub.10 are each independently selected from the group consisting of H and lower alkyl;R.sub.2 is H, hydroxy, loweralkyl, alkoxyalkyl, hydroxyalkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, aryl, or alkylaryl;n is a number from 0 to 2;R.sub.3 and R.sub.4 are each independently selected from the group consisting of H, loweralkyl, loweralkoxy, alkylaryl, aryl, oxyaryl, aminoalkyl, aminoaryl, or halogen; andR.sub.5 and R.sub.6 are each independently selected from the group consisting of H, loweralkyl, aryl, alkylaryl, aminoalkyl, aminoaryl, halogen, oxyalkyl, oxyaryl, or oxyarylalkyl; or a phamaceutically acceptable salt thereof. The compound of Formula I is administered in an amount effective to treat the condition.The present invention also provides compounds useful for the treatment of Pneumocystis carinii pneumonia and Giardia lamblia.