The invention relates to the use of derivatives of E-type prostaglandins as EP₂ agonists, in general, and, in particular as ocular hypotensives. The PGE derivatives used in accordance with the invention are represented by the following formula I: ##STR1##

wherein the hatched segment represents an bonds, the solid triangle represents a bond, the wavy segments represent or bond, dashed lines represent a double bond or a single bond, X is selected from the group consisting of hydrogen and halogen radicals, R³ is heteroaryl or a substituted heteroaryl radical, R¹ and R² are independently selected from the group consisting of hydrogen or a lower alkyl radical having up to six carbon atoms, or a lower acyl radical having up to six carbon atoms, R is selected from the group consisting of CO₂R⁴, CONR⁴₂, CH₂OR⁴, CONR⁴SO₂R⁴, P(O)(OR⁴) and ##STR2##

wherein R⁴ is selected from the group consisting of H, phenyl and lower alkyl having from one to six carbon atoms and n is 0 or an integer of from 1 to 4.