In this work were presented the results of pharmacodynamic research concerning the acute toxicity of some essential oils used in aromatherapy. The essential oils used in this study were: firtree oil (Abietis aeth.), thyme oil (Thymi aeth.), clove oil (Caryophylli aeth.), eucalyptus oil (Eucalypti aeth.), lavender oil (Lavandulae aeth.), peppermint oil (Menthae aeth.), camomile oil (Chamomillae aeth.) and cinnamon oil (Cinnamomi aeth.).

To experimental groups of mouses were given succesive doses between 100% letal dose (the least dose in that succumb all the animals) and the highest tolerated dose (the highest dose in that do not succumb any animal). The behaviour and death of experience animals were been observed in 48 hours and watched for 14 days. The essential oils not diluted were given intraperitoneal.

The symptoms observed to the mouses trated with essential oils (at toxic dose) are : central hyperexcitability (2 minutes, noteworthy to mint), catalepsy, tachycardia, jerky breathing, ataxia, opistotonus and death.

The acute toxicity, expressed in DL 50 (g/kgc) is very high to clove oil (DL 50 = 0.697) and thyme oil (1.063), raised to eucalyptus oil (DL 50 = 2.874), peppermint oil (1.760) and cinnamon oil (1.611), and lower to lavender oil (6.370) and chamomile oil (6.758).

The toxicity degree (expressed through the relation between the effective dose and toxic dose) is very small to all the essential oils studied from this viewpoint. So, these essential oils don't have a therapeutical risk at daily administration in some pharmaceutical products (capsules, ointments).