The aim of this study was to correlate central corneal thickness measurements obtained using optical as well as ultrasound pachymeters and high-frequency ultrasound biomicroscopy (UBM), assuming UBM as reference. Each measurement was performed on 32 patients (60 eyes) by three observers unaware of the other's results, on 3 different days. Pearson correlation was used. A strong correlation was found between UBM and ultrasound pachymetry measurements (r=0.858), a weaker one between UBM and optical pachymetry (r=0.506). Optical versus ultrasound measurements were poorly correlated (r=0.540). Each correlation was statistically significant (p<0.001). UBM can be used as an accurate and reproducible method for determining corneal thickness.