Studies assessing the potential negative consequences of radiocollars on endangered mammals are few. No such studies have been conducted on giant panda (Ailuropoda melanoleuca), an endangered species potentially sensitive to invasive monitoring technologies and handling. Lack of knowledge about the effects of radiocollars and concern for the well-being of radiocollared pandas led to a moratorium on radiocollaring the species in the wild in 1995. To assess the potential effect of radiocollars on the behavior of giant pandas, 4 captive giant pandas (2 male, 2 female) were immobilized and fitted with radiocollars during February and March 2000, just prior to the mating season. We evaluated potential behavioral and endocrine indices of stress daily for 2 weeks before and after immobilization and attachment of radiocollars. We found no significant change in stereotypic behaviors, activity levels, or cortisol levels for any of the 4 individuals. Both adult radiocollared pandas mated successfully. Our results suggest that any potential short-term negative effects from radiocollaring giant pandas are negligible, and with proper planning and use, radiotelemetry can be safely utilized in the study of free-ranging giant pandas.