There are several inherited, (not present at birth), health issues (problems) where Cavaliers are prone to.  These include but are not limited to: heart, eye, hip dysphasia, and patellar luxation (clipping kneecaps), the "big four" as some refer to them as.

It may be possible that some of these area may be caused by other than genetic factors but until there is absolute proof that the problem is cause solely by the environmental factors we as breeders must test and evaluate every cavalier we own, and provide that information to all.
Genetics traits of all kinds do not necessarily show up in every generation, therefore it has become apparent that we must continue to test even if parents and grandparent show clear.  While testing is no guarantee of good health, it is the best that responsible breeders can do at this time to try and improve the health of our canine friends.

Mitral Valve Disease (MVD)  There are several diseases that affect the mitral valve, but the most common one with Cavaliers is degeneration of the mitral valve (the leaflets or cusps which make up the valve may have contracted and curled back on themselves allowing the valve to leak).  When the valve does not close completely, it allows a back flow of blood back into the chamber, called mitral regurgitation.  With mitral regurgitation the blood leaks from the left ventricle into the left atrium of the heart causing it to enlarge.  With enlargement of the left atrium, it can lead to enlargement of the left ventricle.  When the heart becomes enlarged, the dogs may occur some symptoms such as coughing, exercise intolerance, retaining fluid, etc.  With severe mitral regurgitation not only is there significant increase in the left side of the heart, but it is frequently accompanied by varying degrees of congestive heart failure.

It is very important that the parents of the puppy you are looking at were checked by a Cardiologist because mitral regurgitation occurs with such velocity that it produces turbulence, which is detected as a systolic murmur which is heard between the first and second heart sounds.  Most vets are not trained to hear a systolic murmur, but the Cardiologist specialize in this area.

  A Reputable Breeder will have their breeding dogs Certified by a Cardiologist and this will accompany the puppy to their new home.  If the breeder you are speaking with does not have a certification on the puppy's parents, most likely they do not test for this.

Eye Problems:  Cavaliers should have their eyes examined annually by a veterinary ophthalmologist.  The two area that do effect cavaliers are:

    Retinal Dysplasia is an abnormal development of some of the visual cells of the    retina, eventually leading to blindness.  There is no cure for this.  It can be discovered by a Ophthalmologist at a few weeks of age.

    Entropion is where the eyelid folds abnormally and the lashes turn in on the eye and irritate the eye.  The  lower lid is most often the problem.  This can be treated surgically and if left untreated the vision can be threatened and it can lead to corneal ulceration.  Entropion could be hereditary, however on CERF forms it is referred to a Category A = breeders discretion

Canine Hip Dysplasia (CHD) is the malformation and degeneration of the coxofemoral joints.  It is similar to arthritis in people and is one of the most common ailments in dogs.

The femur, or thigh bone, consists of the head (femoral head) and the neck (the part of the femur that joins the long shaft of the bone to the head).  The acetabulum forms the socket part of the joint and it is in this socket that the femoral head rests.  Poor congruence between the femoral head and acetabulum creates abnormal forces across the joint, interferes with normal development and overloads the articular cartilage causing microfractures and degeneration joint disease. 

 Some common symptoms of the disease are pain, difficulty moving, lameness, difficulty getting up, difficulty in sleeping if they have to lay on their particular hip.  The only way to know if your dog has CHD is to have them x-rayed by your vet.

These x-ray are then sent to OFA for diagnosis by a board certified veterinary radiologist.  A preliminary report can be returned if the dog is under the age of two. At the age of 2 or older a permanent OFA certificate with an OFA registry number can be issued.  Only by breeder / owners having x-ray taken and submitted into a control data base, will an important step be taken towards understanding and controlling this problem

on-line information:   http://www.offa.org

Patellar Luxation is the slipping of the patella or knee cap.  The patella is a small bone that is held in place by ligaments that shield the front of the stifle joint and should be located in the center of the knee joint.   As the knee joint is moved, the patella slides in a grove in the femur.  A luxating patella is a knee cap that moves out of the groove in the femur.

The patellar may dislocate toward the inside, called medial, or outside, called lateral, of the leg.  Medial patellar luxation is present at birth and can affect either or both legs.  Laterally luxating patellas are often the result of  trauma and can affect any pet.  Diagnosis is made on physical examination by a regular veterinarian, who manipulates the patella's following guidelines sets up by OFA -- Orthopedic Foundation for Animals.  This is done annually..