Dermatomyositis is an inflammatory myopathy characterized by proximal symmetrical muscle weakness with a characteristic cutaneous eruption. Population-based cohort studies provide evidence of an increased frequency of cancer in dermatomyositis patients. Many signs and serology tests have been suggested as markers for malignancy in dermatomyositis. We performed a case-control study on the patients admitted in our institutions for dermatomyositis. Clinical and laboratory data were collected and statistical analysis was performed to reveal important predictive signs of malignancy in dermatomyositis. We found no statistical difference in the clinical or laboratory parameters between the dermatomyositis patients with or without malignancy, with the exception of the erythrocyte sedimentation rate. In our study group an erythrocyte sedimentation rate higher than 35 mm/hr was very strongly associated with the presence or the development of a malignancy. Given the high positive and negative predictive values observed in our study, erythrocyte sedimentation rate evaluation using this cut-off point could be very useful in alerting dermatologists to the need for more in-depth diagnostic procedures in dermatomyositis patients.