A rotating quartz crystal microbalance is employed to study the effects of the additives sodium dodecyl sulfate (SDS) and saccharin during the pulsed deposition of Cu-Co alloys. SDS promotes Co displacement by Cu during pulse off-times, while saccharin impedes this process. On-time current efficiencies for pulsed deposition are lower than those during de deposition, particularly for SDS-only electrolytes. Off-time areal mass increases in SDS-only electrolytes are much larger than those expected from the displacement of Co by Cu and exhibit a square root dependence on the electrode rotation rate; other electrolytes do not display this behavior. Assuming these mass increases are due to SDS incorporation yields inclusion densities that are consistent with other metal/additive systems previously characterized in the literature. The interaction of SDS and saccharin during pulsed deposition is discussed.