Very little is known regarding the release patterns or circulating titers of neuropeptides in crustaceans, in particular those concerned with regulation of molting hormone (ecdysteroid) synthesis- molt-inhibiting hormone, (MIH) and crustacean hyperglycemic hormone, (CHH), which is also an adaptive hormone, centrally important in carbohydrate metabolism. Furthermore, the currently accepted model of molt-control is founded upon an untested hypothesis suggesting that molting can only proceed following decline in MIH titer. Accordingly, we have measured simultaneous circulating neuropeptide profiles for both MIH and CHH by RIA of purified hemolymph during the molt-cycle, at fine temporal scale during day/night cycles and seasonally. For CHH we additionally determined release patterns following physiologically relevant stress. Results show that both hormones are released exclusively and episodically, rather than continuously, with notably short half-lives in circulation, suggesting dynamic and short-lived variations in levels of both hormones. During the molt cycle, there are no overt changes in MIH titer, excepting a massive and unprecedented increase in MIH during late premolt- just before ecdysis. The function of this hormone surge is unknown. Treatment with various stressors (hypoxia, temperature shock) showed that CHH release occurs extremely rapidly, within minutes of stress. Release of CHH following stressful episodes during premolt, (when gut endocrine cells synthesize large quantities of CHH), is exclusively from the sinus gland: CHH from the gut is never involved in the stress response. The results show a hitherto unsuspected dynamism in release of MIH and CHH, and suggest that currently accepted models of molt control must be reconsidered.