There are many hypotheses about the biological aging. Some error and programme hypotheses are explained and compared with another by examples. The action of stochastic and genetic factors is acknowledged generally, but there are different opinions on the question about a genetic "programme". At the same time there is an effort to integrate some alternative conceptions. By increasing appreciation of evolutional aspects too the interest are pointed out to biological longevity assurance mechanisms and their importance for the maximum lifespan of species or individuals.