In-place tests are performed typically on concrete within a structure@ in contrast to tests performed on molded specimens made from the concrete to be used in the structure. Historically@ they have been called nondestructive tests because some of the early tests did not damage the concrete. Over the years@ however@ new methods have developed that result in superficial local damage. Therefore@ the terminology in-place tests is used as a general category that includes those that do not alter the concrete and those that result in minor surface damage. In this Report@ the principal application of in-place tests is to estimate the compressive strength of the concrete. The significant characteristic of most of these tests is that they do not directly measure the compressive strength of the concrete in a structure. Instead@ they measure some other property that can be correlated to compressive strength (Popovics 1998). The strength is then estimated from a previously established relationship between the measured property and concrete strength. The uncertainty of the estimated compressive strength depends on the variability of the in-place test results and the uncertainty of the relationship between these two parameters. These sources of uncertainty are discussed in this Report.In-place tests can be used to estimate concrete strength during construction so that operations that require a specific strength can be performed safely or curing procedures can be terminated. They can also be used to estimate concrete strength during the evaluation of existing structures. These two applications require slightly different approaches@ so parts of this Report are separated into sections dealing with new and existing construction.A variety of techniques are available for estimating the in-place strength of concrete (Malhotra 1976; Bungey 1989; Malhotra and Carino 1991). No attempt is made to review all of these methods in this report; only those methods that have been standardized by ASTM are discussed. Teodoru (1989) prepared a compilation of national standards on in-place test methods.