During or after construction of concrete structures, assessments of in-situ compressive strength are normally required in cases of non-com- pliant cube samples or in cases where doubts exist with regards to the in-situ concrete quality. In cases where concrete production (mix design, batching, mixing, delivery) and concrete element manufacture (casting, compaction, curing) are done by different parties, as is com- monly the case with Readymix concrete, core testing can provide a means of identifying the origin of the problem when in-situ concrete quality is lower than expected. The method of testing concrete cores for compressive strength is relatively straightforward. However numer- ous factors that may have an influence on the test results need to be taken into consideration in order to analyse the results correctly. This paper presents an overview on the procedures of core testing and analysis, emphasising the different aspects that need consideration for proper interpretation of test results.