Laboratory computers permit detection and discrimination thresholds to be measured rapidly, efficiently, and accurately. In this paper, the general natures of psychometric functions and of thresholds are reviewed, and various methods for estimating sensory thresholds are summarized. The most efficient method, in principle, using maximum-likelihood threshold estimations, is examined in detail. Four techniques are discussed that minimize the reported problems found with the maximum-likelihood method. A package of FORTRAN subroutines, ML-TEST, which implements the maximum-likelihood method, is described. These subroutines are available on request from the author.