Missing regions in X-ray crystal structures in the Protein Data Bank (PDB) have played a foundational role in the study of intrinsically disordered protein regions (IDPRs), especially in the development of in silico predictors of intrinsic disorder. However, a missing region is only a weak indication of intrinsic disorder, and this uncertainty is compounded by the presence of ambiguous regions, where more than one structure of the same protein sequence "disagrees" in terms of the presence or absence of missing residues. The question is this: are these ambiguous regions intrinsically disordered, or are they the result of static disorder that arises from experimental conditions, ensembles of structures, or domain wobbling? A novel way of looking at ambiguous regions in terms of the pattern between multiple PDB structures has been demonstrated. It was found that the propensity for intrinsic disorder increases as the level of ambiguity decreases. However, it is also shown that ambiguity is more likely to occur as the protein region is placed within different environmental conditions, and even the most ambiguous regions as a set display compositional bias that suggests flexibility. The results suggested that ambiguity is a natural result for many IDPRs crystallized under different conditions and that static disorder and wobbling domains are relatively rare. Instead, it is more likely that ambiguity arises because many of these regions were conditionally or partially disordered.Abbreviations: CASP, critical assessment of protein structure prediction; DisProt, a database of proteins with experimentally validated intrinsically disordered regions; DSSP, define secondary structure of proteins; IDP, intrinsically disordered protein; IDPR, intrinsically disordered protein region; MoRF, molecular recognition feature; PDB, protein data bank.Additional Supporting Information may be found in the online version of this article.The authors declare no competing interests.Brief Statement: This study demonstrates a novel way of examining missing regions in the Protein Data Bank (PDB) where multiple PDB structures are available for a single protein sequence and these structures show conflicting information between observed and missing residues. We found that ambiguity in the structural properties of a given region is common and the degree of ambiguity is proportional to the propensity toward disorder. Furthermore, we show that static disorder and wobbling domains are probably rare, and it is likely that most ambiguous regions are conditionally or partially disordered.