High-frequency ultrasound biomicroscopy (UBM) is a new method which allows in vivo visualisation of anterior segment structures with high resolution but limited penetration. Using this modality we wanted to examine the ciliary body and measure its total length and depth and look for correlations with the axial eye length. A special technique with external markers was developed to measure the total length of the ciliary body using two UBM pictures. In 83 patients the mean ciliary body length was 5.2 mm nasally and 5.7 mm temporally. The depth of the ciliary body was 1.2 mm nasally and 1.4 mm temporally. A correlation could be demonstrated between the axial eye length and the ciliary body measurements. As our measurements are reproducible and consistent with recent histological studies, high-resolution UBM can be regarded as a reliable method for in vivo visualisation and quantitative analysis of the ciliary body.