The use of radio telemetry has been accepted as a standard method with which to monitor foraging trip duration in penguins by the CCAMLR (Commission for the Conservation of the Antarctic Marine Living Resources) Ecosystem Monitoring Program (CEMP). This paper reports on: (i) the effects of radio transmitter attachment on nest attendance, foraging trip duration, nest failure, and reproductive success in chinstrap penguins; (ii) differences in these parameters when transmitters are applied to one or both members of a breeding pair; and (iii) variability in foraging patterns of penguins unencumbered by transmitters within the brood period. This study was conducted from December 1990 to January 1991 in a discrete chinstrap penguin colony composed of 666 nests on Seal Island, South Shetland Islands. In total, one member of each pair at 20 nests and both members of each pair at 10 nests were equipped with a radio transmitter, 120 nests were used as a control group. The results of this study demonstrate that, for the size of transmitter used (1.4 cm² front section area); there may be no difference between trip durations obtained by applying the transmitters to one or both members of a breeding pair. However, when all parameters of reproductive success were measured, it was revealed that nests with both members equipped with a transmitter fared worse than both the control group and the group with only one member equipped with a transmitter. Several of the differences in those parameters were shown to be statistically significant. It is therefore recommended to use instruments on only one member of each breeding pair in studies utilising CEMP Standard Methods.