RESUMO: "Estudo preliminar das propriedades moluscicidas e larvicidas de alguns óleosABSTRACT: This study aimed to evaluate the molluscicidal and larvicidal activity of some essential oils and phytochemicals from medicinal plants. Molluscicide and larvicidal activity were determined by, respectively, the lethality bioassays using Artemia salina Leach. Artemiidae and Aedes aegypti L. Culicidae larvae. Essential oils from Eugenia uniflora L. Myrtaceae, Laurus nobilis L. Lauraceae, Origanum vulgare L. Lamiaceae and the phytochemicals α-pinene and eugenol presented citotoxicity toward Artemia salina with CL 50 values between 9.59 and 253.43 µL/mL. Essential oils from E. uniflora, M. piperita, O. vulgare and R. officinalis showed embryotoxicity on Aedes aegypti larvae with a viability inhibition between 40 and 100%. These results show the bioactivity of the assayed essential oils and phytochemicals and, partially, justify their insertion in further evaluation in order to establish a safe exploitation of their biological potentiality.