If you made it this far, you are probably seriously considering owning a mastiff and are proceeding on a search for a quality puppy. When I say quality, I am not refering only to whether a puppy has show potential, but to how physically and mentally healthy it is. When making any large investment (and a Mastiff is definitely a large investment of money and time) you need to take the time to shop around and see who has what you are looking for.
There are certain tests that you should be aware of that help determine how healthy the parents are. Unfortunately, all of these tests only examine the outward appearance of the dog but cannot truly certify that the dogs do not genetically carry the diseases. Therefore, none of these tests are a guarantee that the puppies will be perfect, but they are the best way to reduce your risks.
OFA evaluates x-rays of hips and elbows for the presence of hip and elbow deformities, especially dysplasia. Hip dysplasia is a crippling joint disease that is especially a problem in large and giant breed dogs (such as the Mastiff). There are some surgical methods to help correct the problems but they are costly and painful. OFA has booklets on bone and joint problems that can be obtained from them for more information.
CERF registers dogs who have been examined by a board certified ophthalmologist and certified to be clear of any eye defects that the CERF recognizes as genetic. There are some defects which are present in the Mastiff that are not recognized by the CERF, so possibly obtaining copies of the exam sheets from the breeder and having the sheets interpreted by a qualified veterinarian can help determine which defects can be considered as genetic.
Von Willebrand's Disease and thyroid testing are two other tests commonly performed. Von Willebrand's Disease is a bleeding disorder that causes abnormal bleeding that can be dangerous during surgery and can be indicative of autoimmune disorders. Low thyroid is a common problem in Mastiffs and causes such things as immune problems, allergies, skin problems, and breeding problems. Low thyroid can be treated with medication, but it can be a nuisance.
Most breeders will perform some or all of these tests, please take the time to ask first.
There are different titles for conformation or obedience a dog can obtain through various dog organizations and it is not necessary for the parents to have any. However, titles do suggest that the breeder is interested in promoting and improving the breed. They also suggest that the dog has done more than just lay around the house, and has been able to go out in public. Temperament tests such as the C.G.C. Program (Canine Good Citizen) are also a statement as to the mental stability of the parents. The importance of good temperament can not be stressed enough for a dog as large as a Mastiff.
Do not be surprised at how extensive some sales contracts can be. Most Mastiff breeders understand the breed and know what needs to be done to raise a healthy, well-behaved dog that will exist peacefully in your home. Puppy training is a common requirement in the contract and should be taken seriously and followed. Other restrictions and requirements are put into contracts to help prevent bad situations from arising, such as a spay/neuter requirement for a puppy going to a pet home. If the animal is not going to be used for breeding, spaying or neutering will help decrease the risk of certain diseases as the dog ages and help increase life span. Most breeders also have guarantees in their contracts for that (hopefully) rare instance that a puppy has a genetic disease. Always ask a breeder about their contract and don't be afraid to question certain items you may be unsure about.
Most people have problems locating good breeders since most do not advertise. The above listing of breed clubs will give you a place to start. They will be willing to give you a listing of breeders within your area to help you get started. Many breeders can also refer you to other breeders they may know in the area. Shop around, find out all you can about each breeder and what they are producing. You may have to wait a year or two to get a puppy from a responsible breeder, but it is well worth the wait to find a quality Mastiff that will be a joy to live with.