Numerous concrete street pavements in St. Charles County, MO, are exhibiting pattern cracking at the wearing surface along with severe joint deterioration. Petrographic examinations performed on cores removed from the distressed pavements have revealed that the distress is related to alkali-aggregate reactions associated with the coarse aggregate. Petrographic examinations and testing also were performed on a bulk coarse aggregate sample obtained from a local quarry. The coarse aggregate is a crushed argillaceous dolomitic limestone, which is Mississippian in age. The dolomitic limestone has the classic composition and texture associated with alkali-carbonate reactivity, although the aggregate also contains individual chert particles and small amounts of quartz, chert, and chalcedony within the dolomitic limestone. The petrographic examinations showed that both alkali-carbonate reaction and alkali-silica reaction are occurring in the concrete. The examined pavements were placed from 2003 to 2014.