A logical and thorough clinical investigation should provide the best basis for the diagnosis of skin diseases. Where no diagnosis can be reached despite a full range of investigations, the clinician can justifiably attempt symptomatic treatment, but it is always better to focus treatment on a specific condition based on properly accumulated and tested clinical evidence. Unfortunately, in equine dermatology there are few text descriptions of the majority of the conditions encountered in practice. While a few diseases are well recognized, there is still little consensus on the best treatments for many of them. Individual veterinarians will have treatments that they rely on, but frequently the same treatment applied by another person inexplicably fails to work in the same way. In dermatology cases, there is no substitute for experience. Referencing to quality textbooks and to colleagues who might have encountered the condition before is often advisable. Unusual presentations are frequently encountered in horses. For example, there are many manifestations of the pemphigus group of diseases, and not all will have a clear diagnostic pathway. It is important to remember that the skin is one of the biggest organs in the body and yet little is known of its function and pathology! While there are many significant primary dermatologic conditions, there are also important systemic diseases that have more or less pathognomonic secondary dermatologic signs; this makes the proper clinical examination even more imperative. One of the biggest problems with equine dermatology is the dearth of scientific reports. Many experienced clinicians have much useful information, but this may never reach the rest of the profession. Also there are few useful reference textbooks dedicated to the equine species. Equine dermatology most likely suffers the most of all disciplines in this respect. As a result, every clinician is expected to reinvent the wheel! There is a need for publications and discussions about the problem cases; even the commonest skin diseases are poorly understood. To make the most use of the supporting specialties of microbiology and pathology, it is important to involve the relevant specialists in the diagnostic process. This means that these specialists must have as much information as they can get; it helps enormously if a photograph can be taken of the disease. Without such information, pathologists and microbiologists may make gratuitous statements about treatment options. For example, a biopsy from an upper eyelid lesion might be easily diagnosed as a sarcoid, and any statement concerning wide surgical excision might be both misleading and nonsensical but would be totally avoidable had the specialist been provided more information. The approach to the dermatologic case requires a logical and exhaustive clinical investigation involving a thorough history and a detailed clinical examination. Diagnostic tests should be carefully selected to rule-out or confirm a suspected diagnosis. Frequent reexaminations are often required because it is sometimes difficult to establish the primary condition: this is often due to extensive self-inflicted trauma or iatrogenic interference by the owner. By proceeding in a systematic and stepwise manner, equine ambulatory clinicians can frequently bring dermatologic problems to a successful resolution.