A value of 8.8 μg/mL was measured for the intrinsic solubility of indomethacin. Evidence of a form with a solubility of about 77 μg/mL was also obtained. Solubility measurements were conducted using the CheqSol and Curve Fitting methods using a maximum pH of 9. It is also demonstrated that a published intrinsic solubility of 410 μg/mL was in error due to decomposition of indomethacin at pH 12. The decomposition of indomethacin at pH 12 was investigated. Decomposition products comprising p-chlorobenzoic acid and 5-Methoxy-2-methyl-3-indoleacetic acid were isolated and characterised.