Last quarter I gave a presentation in our Introductory Epidemiology course on the late Austin Bradford Hill and his seminal talk on causal inference in population health research. I had a great opportunity to contrast Hill’s original observations with their evaluation by John P. A. Ioannidis and offer my own interpretations. I thought my slides might be useful to others outside our (relatively) small class, so they are posted below, with references at the end.