This manuscript discusses a prototype image-guided robotic system that is currently under development at The Johns Hopkins University. This system is intended to allow percutaneous delivery of surgical devices as well as therapeutic agents to soft tissue and bone lesions. The proposed system has many potential applications including the treatment of liver cancer, which is an attractive application of the technology. The purpose of the system is to allow more accurate and precise delivery of therapeutic modalities than can be achieved freehand by the physician. This will allow the treatment of lesions that are smaller than 2 cm in diameter which is not possible with current freehand percutaneous techniques. The system will also allow rapid re-targeting for multiple lesions and optimal therapy distribution over a treatment volume through delivery of a precise pattern of treatment, both of which are difficult to accomplish manually. Moreover, we hope to stimulate development of novel therapies which can take full advantage of the substantially improved accuracy in placing a therapy delivery device within the volume of the organ of interest. The system has the potential to replace major surgery thereby reducing the associated morbidity and mortality as well as reduce the cost of treatment. Additionally, the minimally invasive procedure allows treatment of those patients for whom surgery is contraindicated. In vitro phantom studies show that the system is capable of placing small "treatment" spheres (representing brachytherapy seeds) with a mean accuracy of 0.52 mm with a 99% confidence interval of [0.38 mm - 0.66 mm] for the mean estimate. The maximum error encountered with these studies was 0.9 mm. These studies encourage us to move forward toward in vivo studies. While we are focusing on the liver in this manuscript, the technology can be used in other soft tissue systems, such as the kidney , with minor modifications. In this manuscript, we discuss the design and testing considerations of the prototype system as well as briefly discussing planned future improvements to the system.