As an ideal, altruism has long enjoyed privileged status in medicine and medical education. As a practice, altruism is perceived to be in decline in the current generation. A number of educational efforts are underway to reclaim this "lost value" of medicine. In this paper we explore constructions of altruism over a defined period of time through a content analysis of the Canadian and Australian Medical Associations (CMA and AMA respectively) Codes of Ethics. We analyzed all editions of both Codes (1868-2004), using a content analysis approach, including thematic analysis. We coded as altruistic or non-altruistic, respectively, statements in which the interest of the patient is placed ahead of the physician's and statements in which the interest of the physician is given primacy. We examined the pattern of appearance and disappearance of these statements over time. We identified 13 altruistic and 2 non-altruistic statements across all editions. There is a gradual and uneven loss of altruistic content over time. The CMA Codes of 1938, 1970 and 2004 and the AMA code of 1992 represent significant change points. The most recent versions of both Codes contain only 1 altruistic statement and both non-altruistic statements. We conclude that altruism appears to be a fluid and changing concept over time. Loss of altruism is not merely a current generational issue but extends through the past century and is likely due to political and social forces. These results call into question current educational attempts to reclaim altruism, and point to the social evolution of the ideal.