Most ADCs have separate analog ground (AGnd) and digital ground (DGnd) pins, but too many engineers, and, unfortunately, too many data sheet writers as well, are uncertain how they should be connected. The lecture considers the nature of the currents flowing in these pins, the vulnerabilities of precision data converters to internal and external noise, and the effects of various grounding and decoupling configurations, and suggests, and justifies, a grounding scheme which gives the best possible converter performance in the vast majority of cases.