In human vision, mechanisms specialized for encoding static form can signal the presence of blurred forms trailing behind moving objects. People are typically unaware of these motion-blur signals because other mechanisms signal sharply defined moving forms. When active, these mechanisms can suppress awareness of motion blur. Thus, although discrepant form signals can be produced, human vision usually settles on a single coherent perceptual outcome. Here we report a dramatic exception. We found that, in some circumstances, static motion-blur form signals and moving-form signals can engage in a dynamic competition for perceptual dominance. We refer to the phenomenon as spatiotemporal rivalry (STR). Our data confirm that moving- and static-form mechanisms can generate independent signals, each of which can intermittently dominate perception. STR could therefore be exploited to investigate how these mechanisms contribute to determining the content of visual awareness.