The objective of this study was to compare the accuracy of self-reported skin cancer risk outcome measures proposed as standards by prevention experts to aggregated estimates of behavior from weekly diaries. Weekly electronic diaries of ultraviolet radiation (UVR) behaviors, initially validated by comparison with daily electronic diaries, were used to assess the accuracy of commonly used end-of-summer self-reported measures among 250 adults. Results revealed low biases, and good correspondence between simple open-ended self-reported estimates of days outside, hours outside, sunbathing days and hours, and days outside when not protected by either sunscreen, long-sleeved shirts, hats, or shade. Rating scale measures commonly used in the current literature and those recently recommended as standards by a workshop of experts showed evidence of being non-interval and lacking precision for more frequent behavior (e.g., >1 h sun exposure daily). These data indicated that open-ended frequency self-reports of skin cancer risk behaviors that follow procedures designed to increase accuracy were reliable over a summer-long period.