New Jersey's carbonate rock study was undertaken to develop a procedure to evaluate local ourcc for potential alkali carbonate reaction. Laboratory tests were performed on rock samples obtained from eight local sources with unknown reactive characteristics and three control samples with well-known reactive characteristics. The screening criteria described in the paper identified the known reactive sources, and also indicated that some local ource are potentially reactive at higher alkali levels. It is recommended that use of carbonate aggregate be conditioned on d mon rrated nonreactivity under the described battery of tests. As a precautionary mea ure, low-alkali cement (alkali levels less than 0.7 percent) hould be used with carbonate rock aggr~ g. ate to mitigate the effect of any failure to detect aggregate reactivity.