Purpose: An item analysis of Bishop's (1983) Test for Reception of Grammar (TROG) in its French version (F-TROG; Lecocq, 1996) was conducted to determine whether the difficulty of items is similar for participants with or without intellectual disability (ID). Method: In Study 1, responses to the 92 F-TROG items by 55 participants with Down syndrome (DS), 55 with ID of undifferentiated etiology (UND), and 55 typical children (TYP) matched on their F-TROG total score were compared using the transformed item difficulties method, a statistical approach designed to detect differential item functioning (DIF) between groups. In Study 2, an additional comparison involving 526 TYP participants and 526 participants with UND was conducted to increase the statistical power of the analysis. Results: The difficulty of items was highly similar whatever the sample size or clinical status of participants. Fewer than 3.5% of the items were flagged as showing DIF. Conclusions: Tests such as the TROG can be used with confidence in clinical practice as well as in research studies comparing participants with or without ID. Methods designed for investigating potential internal test bias--such as done here--should be more regularly employed in the developmental disability field to affirm the absence of DIF.