The extensive information on the neuroanatomy, development and genetics of Caenorhabditis (C.) elegans make it an ideal candidate model system for the analysis of the mechanisms underlying learning and memory. A first step in this analysis is the demonstration of the capacity of C. elegans to learn. In these experiments non-associative learning in C. elegans was investigated by observing changes in reversal reflex response amplitude to a mechanical vibratory stimulus. The results from these studies of non-associative learning show that C. elegans is capable of short-term habituation, dishabituation and sensitization, as well as long-term retention of habituation training lasting for at least 24 h. These findings set the stage for detailed developmental, genetic and physiological analyses of learning and memory.