The application of randomization tests for statistical determination of the significance of experimental manipulations on single cells and other types of single units in neuroscience is described. Applications of standard parametric tests like analysis of variance (ANOVA) and t tests to data from single-subject experiments have been severely criticized for lack of validity and those criticisms are relevant to parametric statistical tests for data from other types of single-unit experiments. A broad class of statistical tests known as randomization tests, on the other hand, has been free of such criticism. Randomization tests have been applied to data from various types of single units in neuroscience, where their validity in the absence of random sampling makes them especially valuable. Until the advent of computers, the computational requirements of randomization tests rendered them impractical. Randomization test computer programs are now readily available. Procedures for access to a public domain program are given in the text.