Aspects of the transduction processes employed by gustatory, olfactory and carotid chemoreceptor cells, as well as the chemosensitivity of certain cutaneous mechanoreceptors are considered in this publication. Two general classes of sensory receptors are represented by these systems. Simple receptors are specialized primary afferent neurons, such as olfactory receptor neurons, while composite receptors consist of pre-neural receptor cell(s) in association with primary afferent neurons, such as are found in the gustatory, carotid chemosensory and Merkel cell mechanoreceptor systems. A diversity of mechanisms are used by sensory receptors to transduce input. Simple receptor properties considered include the role of multiple transduction cascades in odorant detection (squid and zebrafish), and potential modulation by a GABAergic receptor (lobster). Composite receptor properties examined include signal transduction mechanisms involving phosporylation of specific protein targets, and dynamics of biogenic amine and peptidergic messengers (mammalian carotid chemoreceptors and cutaneous mechanoreceptors). This special issue will be of particular interest to investigators interested in the diversity of transduction mechanisms employed by chemoreceptor cells and to researchers interested in signal transduction mechanisms used by sensory receptors.