We summarize the psychological mechanisms that have been linked to the development and maintenance of medically unexplained symptoms (MUS). Many models postulate that patients with MUS misinterpret physical sensations and show other cognitive abnormalities (e.g., an over-exclusive concept of health) that play a major role in symptom development. While there is strong evidence for the role of cognitive aspects, there is less evidence for their interaction with perceptual features (e.g., perceptual sensitivity, lowered perceptual threshold). Modern neuroimaging techniques show that the expectation of symptoms leads to the activation of brain areas corresponding to symptom perception, while distraction from symptoms reduces brain activity in perception areas. The frequently postulated monocausal organic attribution for physical sensations by patients with MUS needs to be modified, as many patients report multiple symptom attributions, including psychological. Symptom attributions and causal models depend on memorized concepts, and so memory processes need to be investigated in more detail. Aberrations in memory processes not only offer a link to understanding perceptual processes, but are also involved in doctor-patient interaction. This encounter is characterized by unsuccessful medical reassurance, which again involves memory processes. We conclude that psychological mechanisms such as expectation, distraction, and memory processes need to be integrated with biological models to aid understanding of MUS.