In Buddhism the first precept is "Do not kill." This is the one thing that all Buddhist schools agree on.
Please note that in Buddhism the First Precept is unconditional: Whenever there is a conflict among precepts, the First one takes priority.
Also, it is not limited to the taking of the human life, but encompasses all sentient beings. It is not limited to the taking of the life of others: Suicide goes against the First Precept as well.
What about self-defense in Buddhism? Can I kill someone who would otherwise kill me? As mentioned above, the First Precept is about not killing myself as well as others. The First Precept implies the duty of every Buddhist to defend his own life to the best of his ability. Hence, self-defense is not only a possibility but a requirement for every Buddhist. This, no doubt, is one of the reasons for the creation of martial arts in Buddhist temples: They train the Buddhist to protect his own life without the taking of the life of his attacker (at least whenever possible).
The First Precept implies protecting oneself against things that lead to death over a long run, not just direct killing: Such as doing unhealthy things that eventually lead to the deterioration of health and result in an early death.