One characteristic feature of aging in all organisms is the continuous loss of adaptability to environmental perturbations. It is the result of a loss of control over the harmonization of a number of individual reactions which should be in a reciprocally interdependent state ensuring homeostasis. This chapter includes six sections which describe some sensorimotor performance tests that can be used to closely analyze age-related diminishing adaptability. The subareas which regulate and safeguard the functional systems for which the tests are models, are also presented. Procedures for measuring reflexes, muscular strength, motor activity and coordination are described by means of examples, in addition to some methods which are suitable for assessing motor behavior associated with cognitive abilities or the expression of emotional reactions. The concluding chapter discusses the possibilities and limitations of the tests for describing the scheme of stimulus-effect relationships (stimulus perception—central nervous system processing of information —responsiveness of the target organ) and stresses the need for an extensive battery of tests.