This thesis document is a detailed description of the redesign of a breast biopsy needlepositioning system. It describes the current machine and its problem, an outdated drivingsystem, as well as giving a general understanding of taking a breast biopsy. Thisto clarify the topic to the reader and giving them a better understanding and to designa more complete product. This introduction was followed up by a research part aboutcontemporary driving and guiding systems. By the use of a morphology and decisionmatrix as well as a meeting with the company it was soon decided that linear guiderails in combination with a special type of stepper motors was the best solution forthe problem. After this decision was made, the project continued by making a detailedCAD model. The biggest challenge here was making the machine as compact as possible.With the design choices made, the result is a machine which is as compact as it canget. The last stage of the project was doing a verification. This was already partly donein deciding which stepper motors and linear guide rails were suitable. However, checkingif the machine would be able to handle the forces specified in the list of demandsand wishes still had to be done and is executed with the use of FEM. After the FEManalysis was executed it was soon concluded that the stress limit of the aluminum alloywas not reached and the maximum deflection was below the limit. A few demands wereleft untested because it would require a prototype made of its actual components andmaterials used for the production machines.