Ursodiol or ursodeoxycholic acid (UDCA) is a bile acid derivative of cholesterol. Since it can have antioxidant, anti-inflammatory and anti-apoptotic effects, it has mechanisms by which it could slow ALS progression. Here we discuss trials of UDCA in PALS, including the taurine-conjugated form (TUDCA). Some of these trials came out after our ALSUntangled review, and have changed our opinion about UDCA as an ALS treatment.