It is known that a pre-clinical stage may precede the full-fledged form of REM sleep behavior disorder (RBD) and that somniloquy, yelling and limb jerking may be prodromes of RBD. In the present paper, the case of a woman exhibiting both somniloquy and daytime inhibition of speech is discussed. Clinical and polysomnographic findings were consistent with the dual diagnosis of progressive supranuclear palsy (PSP) and preclinical RBD. Severe akinesia and supranuclear palsy of phonation are postulated as likely mechanisms for the inhibition of speech, whereas the overexcitation of the motor system by the RBD process seemed to account for the sleeptalking episodes.