Invasion into the surrounding tissue and bone metastasis is a common feature of advanced prostate cancer. Chromosomal and other genetic or epigenetic abnormalities were aligned to this behaviour mostly by using permanent cell lines, paraffin embedded tissue or primary tumour samples. Both attempts fail to reflect either the original situation or functional information in the patient's tissue. Thus, we developed an improved in vitro assay to follow invasion of prostate cancer cells derived from fresh samples of radical prostatectomy specimens. Fresh tumour samples were applied onto Matrigeltrade mark-coated invasion chambers using a cocultivation model. Invasive growing cells were harvested from the bottom of the membrane or from the underlying gel and further characterized using comparative genomic hybridization. Prostate cancer cells have the capability to invasively grow through the barrier of a Matrigeltrade mark and could easily be sampled in a pad of Matrigeltrade mark. Comparative genomic hybridization revealed characteristic chromosomal aberrations of the invasive growing cells. Noteworthy is their ability to spheroid formation, which allows for further cell propagation by standard cell culture methods. Thus, our improved invasion model is a tool for the sampling of invasive growing cancer cells from fresh human tumour material allowing for functional as well as genetic studies.