Four experiments with rats in an appetitive conditioned magazine entry preparation examined spontaneous recovery after extinction. Spontaneous recovery was obtained 6 days but not 5 hr following extinction; recovery depended on the passage of time but not on the removal of a cue that was featured in extinction or on the reintroduction of early-session cues. A cue featured in extinction attenuated recovery when presented on the test. The attenuation effect depended on the cue's correlation with extinction; a cue featured in conditioning did not attenuate recovery. The extinction cue did not evoke responding on its own, suggesting that it was not a conditioned excitor. Retardation tests and a summation test did not reveal that it was a conditioned inhibitor. The cue might work by retrieving a memory of extinction. Spontaneous recovery thus occurs because the subject fails to retrieve an extinction memory. Other accounts of spontaneous recovery are discussed.