Covert sensitization is the first of a family of behavior therapy procedures called covert conditioning initially developed by Joseph Cautela in the 1960s and 1970s. The covert conditioning procedures involve the use of visualized imagery and are designed to work according to operant conditioning principles. When working with cooperative clients to treat maladaptive approach behaviors, covert sensitization has been found to be a humane and effective alternative to in vivo aversion therapy procedures that employ aversive stimuli such as chemicals and electric shock. This primer describes covert sensitization, provides examples and notes representative research. Guidelines for use and suggestions for further readings are also included.