Milkers' nodules is a self-limited, inflammatory disease which is characterized by the appearance of nodules on the exposed skin surfaces of persons who milk cows. Important features in a consideration of the etiology of the disease will be presented in this report in the following order:(1) historical note; (2) clinical and epidemiological features of milkers' nodules which suggest its etiology; (3) relationship of milkers' nodules to vaccinia; (4) attempts to transmit milkers' nodules experimentally; (5) comment, and (6) summary and conclusions. 1. Historical Note A. Spurious (or False) Cowpox.—The writings of Edward Jenner suggests that the disease which is now called milkers' nodules was either identical with or included in the disorder (or disorders) which Jenner called spurious cowpox. Jenner discussed the subject of spurious cowpox in four of his major writings and in several letters to his contemporaries.7,16