We have previously demonstrated by computer simulation that the relationship of proliferation and motility is likely to influence the morphological pattern of a tumor. Our study of a set of melanocytic skin tumors provided evidence that the assumptions of the model were correct with respect to proliferation. In order to test the validity of the assumptions concerning motility, we injected a tumor cell line with low motility in vitro and a subline of the same tumor cell line with high motility in vitro into the thigh of syngeneic rats. When we evaluated the morphological patterns of the resulting tumors by image analysis and compared them with computer simulations, we found that the differences of the morphological patterns were the same as predicted by the computer model. This finding further supports the concept that estimates of tumor cell proliferation and motility can be derived from the analysis of static histological patterns.