Language testing plays an important role in the identification and monitoring of children with communication difficulties. However, the standardisation of many tests in common use remains far from satisfactory, especially at the lower age ranges. Comparisons between age-equivalent scores and chronological age also raise particular problems. The present paper focuses on the disparity between scores on different tests, in spite of the homogeneity of the group of children studied, and stresses the need for caution in the interpretation of test scores.