Deciding whether a certain cancer patient is suffering from a bone marrow metastasis is quite essential to clinicians. To find a set of explanatory variables of the bone marrow metastasis, we employed the logistic regression analysis on 60 cancer patients with bone marrow metastasis (the case group) and 41 cancer patients without bone marrow metastasis (the control group). These data shown in Append were collected retrospectively from the record of Severance Hospital of Yonsei University College of Medicine from January, 1977 to December, 1985. We could establish a set of decision rules of the bone marrow metastasis specially designed for clinicians based on the explanatory variables of the best fitting logistic regression equation. We also compute the specifity and the sensistivity of our decision rules.