Objective To evaluate intrinsic nodule features predictive of an inadequate report in fine-needle aspiration cytology (FNAC). Design Single-centre cross-sectional study. Methods Between May 2005 and April 2011, 3279 ultrasonography-assisted FNACs were carried out and features of nodules recorded prospectively. Univariate logistic regression analyses were performed to estimate the association between nondiagnostic cytology and variables such as age, gender, single nodule, maximum nodule diameter and estimated volume. Results Inadequate or nondiagnostic samples were reported in 1195 FNACs. All diameters were found to be predictors of nondiagnostic cytology; estimated nodule volume, on the other hand, was not. Nodules with a diameter