||In our studies of the sexual behaviors of Caenorhabditis remanei (C. remanei) and Caenorhabditis elegans (C. elegans), a sex-specific attractant produced by the females of the dioecious C. remanei has been identified. Yet males from both species can be attracted to this C. remanei sex pheromone. Hence, the well characterized C. elegans is therefore selected as the model organism to investigate this sex pheromone induced response. Previously, through genetic analyses and cell-specific ablation experiments, the male-specific response towards sex pheromone in the C. elegans is shown to be coordinated by the neural network which consists of chemosensory AWA neurons, AIZ interneurons and male-specific sensory neurons CEM. Recently, this sex pheromone-mediated behavior is also found to be regulated by various paracrine factors. In this study, a genetic analysis shows that insulin-like growth factor (IGF) and transforming growth factor (TGF)-beta signals are essential for the males to sense sex pheromone. Mutant males with down-regulated paracrine signals are non-responsive toward sex pheromone. Moreover, tissue-specific rescue and knock-down of gene experiments reveal that these paracrine signals are required in the nervous system for the males to perceive the pheromone. The impact of eliminating specific IGF or TGF-beta components on the AWAs, AIZs and CEMs morphologies will also be addressed by fluorescent labeling technology and confocal microscopy. Ultimately, the potential implication of the interplay of paracrine factors and rapid chemosensory processing will also be discussed.