The main reason scientists are currently interested in cloning is because it can be used to grow replacement tissues and organs for people who need transplants.

Although doctors have performed transplant operations for more than fifty years with some success, many patients die and many transplant operations fail because of "tissue rejection".

When any organ or tissue (kidney, skin, heart, even sometimes blood) is put into someone's body the immune system goes on alert and checks to see if the material is foreign or native. This is how your body reacts when a bacteria or virus is found as well. If the cells are not identical to the patient's cells, the body will reject the tissue, attacking it, and causing worse disease for an already sick patient. We try to deal with this now by putting transplant patients on a lot of drugs to suppress their immune system, but this leaves them open to infection or even a strong immune response years down the line when the body realizes it's been tricked.

The power of cloning is that we can grow tissues and organs using your DNA. This means that if someone you knew had a heart attack, we could take some of their DNA and grow them new heart tissue which could be transplanted with no risk of rejection because it is identical to the old heart tissue in every way (except healthier).

Some examples of medical uses of cloning:
(keep in mind that cloning is difficult and many of these methods are decades away from testing)
1) burn victims - new skin can be grown in a lab and grafted in place with no rejection.
2) kidney failure - instead of taking kidneys from close relatives in the hopes that they won't be rejected, a new kidney can be grown and transplanted.
3) leukemia - new bone marrow can be grown from DNA placed into a new stem cell which has no cancerous characteristics and which will not be rejected.
4) genetic disorders - a patient whose DNA has errors in the instructions for making specific organs can have that organ cloned with corrected DNA.

Despite the moral problems with developing cloning technologies, cloning has the potential to dramatically improve the health and life expectancy of transplant patients and will likely provide some relief to patients suffering from hundreds of genetic disorders. This is why doctors and researchers expend so much energy on cloning.

For more information about cloning check out this website:
cloning