To study the effects of various emotions on behavior, psychologists have traditionally used one of a variety of mood-induction techniques. A manipulation check measuring the mood in question is used to determine the success of the mood induction. Evidence indicates, however, that attempting to induce one particular emotion may actually result in arousal of several affects. A series of laboratory studies and one naturalistic observation are reported that demonstrate that so-called standard manipulations for producing particular discrete emotions actually give rise to multiple moods. Even naturally occurring emotions seem to occur in clusters rather than singly. Implications for laboratory study of emotion and the nature of emotional responses in general are discussed.