Sustain talk occupies a structurally indispensable position in the motivational interviewing framework elaborated by William R. Miller and colleagues. Far from being mere resistance or pathological obstruction, sustain talk is understood as the natural linguistic expression of ambivalence — the voice of the status quo speaking alongside, and in dialectical tension with, change talk. Miller’s corpus treats sustain talk not as an opponent to be defeated but as a signal to be heard, reflected, and strategically navigated. The central technical challenge is managing the ratio of change talk to sustain talk across the arc of a session: early conversations are typically dominated by sustain talk, and skillful interviewing gradually tilts that ratio without suppressing the client’s genuine ambivalence. Three principal response strategies receive extended treatment — simple reflection, amplified reflection, and double-sided reflection — each designed to evoke the change-oriented underside of the client’s sustain-talk statement. Discord, a related but distinct phenomenon arising from interpersonal friction rather than intrapersonal ambivalence, is consistently differentiated from sustain talk, though both demand MI-consistent, autonomy-honoring responses. The psycholinguistic dimension is equally significant: research on client speech within MI sessions demonstrates that sustain talk is both predictable and counselor-modifiable, confirming that practitioner behavior can either amplify or attenuate it.