Synthesis of tritium-labeled N-acetyl PGE2 carboxamide (CP-27,987). 
The preparation of N-acetyl PGE2 carboxamide (CP-27,987) regioselectively labeled at C-18 and C-19 with tritium is described.  The overall radiochemical yield was 8.0% at a specific activity of 0.49 Ci/mmole.  The synthesis employed is applicable to the preparation of tritium labeled natural prostaglandins and a variety of analogs.