Almost seven years after the birth of Dolly the sheep shocked scientists and the public, cloning has shown mixed progress. Scientists have achieved it in more than a dozen mammal species but an efficient cloning process still eludes them. Clones are more prone to physical defects than regular animals are. And researchers haven't been able to duplicate monkeys from adult or fetal tissue, a goal that could help medical research.

Does the world need therapeutic cloning research? UN members are preparing to vote on a resolution to ban human cloning.

Researchers have unveiled a new technique that could transform reproductive cloning into a safe, standardized technique for assisted reproduction. They discussed an extra step that could eliminate many objections to the controversial technique.

Human cloning is nearly impossible using current techniques, according to new research that casts further doubt on rogue human cloning efforts.

A newly discovered quirk of primate cell biology suggests that monkeys - and humans - are impossible to clone from adult cells using current techniques.

Cloning humans, or any other primates, may be impossible with today's techniques because of a fundamental molecular obstacle, say scientists trying to understand why attempts to clone monkeys have failed.

Michael Shermer proposes using a variant of Asimov's famous Three Laws of Robotics to resolve the current debate over human cloning.

A smoldering global debate over human cloning is likely to flare following a report this week that researchers in South Korea have for the first time cloned human embryos and used them to produce a type of cell widely regraded as a potential key to treating a range of diseases.

Theraputic cloning, the use of cloning technology for curing disease, is often raised in cloning debates as a positive benefit of human cloning. However, scientists admit the technology is "literally in an embryonic stage."

Kurzweil argues that of all the applications of theraputic cloning, human cloning is the least interesting and least worrisome.