Three dimensional (3D) imaging and analysis facilities have been developed within the 'PICS' general image processing software facility at the Nuclear Medicine Department, Southampton General Hospital. Facilities have been developed for creation of 3D voxel datasets from single photon emission computerised tomography (SPECT), computerised axial tomography (CT) and ultrasound source image data. Facilities included generation of pseudo 3D projection images of the 3D data, with techniques for measurement of parameters such as distance, surface area and volume from 3D images. The accuracy of 3D images and measurements from them have been checked by analysis of phantoms. The 3D imaging and analysis software has been applied to CT, ultrasound and SPECT slice data. CT images of patients presenting with colorectal liver metastases have been processed to isolate tumour tissue and thus obtain measurements of volume and thus percentage hepatic replacement (PHR). Measured PHR compared well with visual estimates within broad categories by qualified radiologists. No clear relation between PHR and total liver volume, or between PHR and survival was observed. 3D images from CT source images of dysplastic hips were analysed to assess acetabular orientation and surface area. The accuracy of measures was checked on cadavers and computer generated phantoms. 3D analysis confirmed the effectiveness of pelvic osteotomy in reducing acetabular anteversion and inclination by rotation of the acetabulum. 3D analysis has been performed on ultrasound sweep images sampled from videotape. In-vivo measurements of placental volume at 16-20 weeks gestation has been performed. The accuracy of volume measurement has been assessed on phantoms and reproducibility by repetition on the same patients. 3D visualisation has been performed on arteries and enlarged biliary trees. The potential of 3D visualisation for treatment planning and education has been illustrated.