We study how retardation leads to interference effects in radiatively coupled plasmonic nanoparticles. We show that inclined illumination through a glass substrate on two plasmonic particles results in either an enhanced field or an attenuated field localized at the position of the first particle. Periodic intensity blinking of the first particle is observed as a function of the particle separation. This phenomenon is nonsymmetric, and almost no blinking is observed on the second particle. The effect is strongest when the illumination angle is chosen such that the optical retardation path in the substrate coincides with the particle distance. Implications of this plasmonic blinking for near-field measurements are discussed. (C) 2009 Optical Society of America