Cavaliers are basically a healthy, sturdy small dog with few, but important health concerns. You should ask the breeder if they test for these health issues.

The most serious health problem in Cavalier King Charles Spaniels is Mitral Valve Disease (MVD). This is a problem with the left or mitral valve of the heart. In this disease, the valve can thicken and degenerate leading to congestive heart failure and eventually death. Although MVD is common in most toy breeds, it is of particular concern in Cavaliers because it may have an unusually early onset with a more rapid progression of symptoms compared to other breeds. MVD has been found in all blood lines and in Cavaliers from all countries; conscientious breeders all over the world regularly check the health of their breeding stock for signs of early onset of this disease before breeding.

While Cavaliers do not commonly have serious eye problems, like all mammals, they can develop cataracts and other eye diseases. Careful breeders have certified veterinarian ophthalmologists check their breeding stock annually.

Another area of concern is luxating patellas (slipping kneecaps). This is a condition when the knee is not stable and can cause lameness. Luckily Cavaliers with good bone and healthy parents generally are not a candidate for this problem.

Hip dysplasia, which is a major concern for large breeds, is not often encountered when the parents and grandparents are strong and healthy.

While Cavaliers can be prone to other diseases that affect other breeds of dogs, there are no additional areas of major concern at this time.

Links to useful Health sites :

List of ACVIM Board-certified Cardiologists by USA State
http://www.vetheart.com/bystate.htm

Orthopedic Foundation for Animals
http://www.offa.org/

Canine Eye Registration Foundation
http://www.vet.purdue.edu/~yshen/cerf.html