We show here that the lin-11 LIM homeobox gene is expressed in nine classes of head, ventral cord, and tail neurons and functions at a late step in the development of a subset of these neurons. In a lin-11 null mutant, all lin-11-expressing neurons are generated. Several of these neurons, however, exhibit neuroanatomical as well as functional defects. In the lateral head ganglion, lin-11 functions in a neural network that regulates thermosensory behavior. It is expressed in the AIZ interneuron that processes high temperature input and is required for the function of AIZ in the thermoregulatory neural network. Another LIM homeobox gene, ttx-3, functions in the antagonistic thermoregulatory interneuron AIY (). Thus, distinct LIM genes specify the functions of functionally related antagonistic interneurons within a neural network dedicated for thermoregulatory processes. Both ttx-3 and lin-11 expression are maintained throughout adulthood, suggesting that these LIM homeobox genes play a role in the functional maintenance of this neural circuit. We propose that particular LIM homeobox genes specify the distinct features of functionally related neurons that generate patterned behaviors.