This paper describes a series of experimental prerequisites in assessments to measure the efficacy of analgesic drugs in healthy man. Of course, there is no doubt that an analgesic has to prove its validity exactly where it ought to help; i.e. in the patient suffering from pain. But to objectify the mode of action, or to measure dose-response functions, to evaluate the optimal therapeutic dosage, or to compare the relative efficacy of the drug tested with known substances--all these investigations can best be performed in a sample of healthy, informed, intelligent and cooperative volunteers, as homogenous as possible. Various kinds of stimuli used in the experimental pain laboratory will be compared with respect to their usefulness in algesimetry; for example the CO2 laser stimulus and the intracutaneous electrical shock. New examples in the analysis of cerebral potentials evoked by painful stimuli will be presented, such as the principal component analysis, the maximum entropy method, and procedures of cerebral potential mappings. It will be shown that frequency transformation of stimulus-induced changes in the electroencephalogram can result in a powerful tool to verify effects even of the so-called weak analgesics, such as acetyl salicylic acid (Aspirin).