Episodic weakness and collapse are common but frustrating clinical problems to investigate. They are frustrating because of the multitude of diseases that can manifest in this way and therefore the multitude of different organ systems that can be responsible for their development. Another challenging aspect of their investigation is that they are often intermittent, frequently occur in specific situations and are rarely observed by the clinician to whom the patient presents. If episodes are reasonably frequent asking the owner to video an episode and observe for specific changes in the patient can be very helpful. In a multidisciplinary hospital these patients can present to one of a number of different services and the initial challenge is often trying to decide which is the most appropriate service for which patient. Important clues can be obtained from the history and physical examination including: when do episodes occur?; is it at rest or on exertion?; does the patient seem to anticipate episodes, or do they occur out of the blue?; is the situation in which episodes occur always similar e.g. sprinting, barking at the postman or defecating?; does the patient lose consciousness?; how long do episodes last and what is the patient doing during the episode?; how rapid is recovery and how long does it take until the patient is back to normal?; is the patient completely normal between episodes?; do the signs seem to lateralise?; are any other clinical signs apparent? Careful physical examination may help to differentiate a patient with a neurological origin of their signs from one with cardiovascular or metabolic origins. Determining the system more likely to be responsible for the signs can allow more targeted diagnostic tests to be performed and prevent unnecessary expenditure on tests that are unlikely to be helpful. These points are illustrated during discussion of different case presentations.