Relativistic plasma masers operating on the anomalous cyclotron-Cherenkov resonance (ω - k||v|| + ωB/γres = 0) and on the Cherenkovdrift resonance (ω - k||v|| - kxud = 0) are capable of explaining the main observational characteristics of pulsar radio emission. Both electromagnetic instabilities are due to the interaction of the fast particles of the primary beam and from the tail of the distribution with the normal modes of a strongly magnetized, one-dimensional electron-positron plasma. In a typical pulsar, both resonances occur in the outer parts of the magnetosphere at rres ≍ 109 cm.