Croton lechleri essential oil has been obtained by steam distillation of fresh stem bark from Amazonian Ecuador adult plants (yield: 0.61 ml/kg [0.061 percent]; density: 1.01 g/ml), and then chemically characterised by GC (Gas Chromatography)and GC-MS (gas chromatography-mass spectrometry). Seventy-four chemicals were detected and identified; the most abundant in descending order, were the sesquiterpenes sesquicineole (17.29 percent), ?-calacorene (11.29 percent), 1,10-di-epi-cubenol (4.75 percent), ?-calacorene (4.34 percent)and epi-cedrol (4.09 percent). Monoterpenes checked with a relative peak area higher than 2.0 percent were ?-pinene (2.01 percent), p-cymene (2.61 percent), limonene (4.20 percent)and borneol (2.67 percent). The structure of the main chemicals were confirmed by GC-MS and 1H NMR analyses. Spectrophotometric 1,1-diphenyl-2-picrylhydrazyl (DPPH)and DPPH-(high performance)thin layer chromatography (DPPH-(HP)TLC)bioautographic assays showed a lower radical scavenging capacity (IC50)with respect to commercial thyme essential oil and BHA (butylated hydroxyl anisole), pointing out, however, that the C. lechleri essential oil fraction, characterised by ?-calacorene, ?-calacorene and ?-cadalene, was the most involved in the bioactivity. Similar results were obtained with ?-carotene bleaching assay, where the IC50 values were 0.291 ± 0.024 mg/ml for C. lechleri essential oil, 0.164 ± 0.013 and 1.34 × 10?4 ± 10?5 mg/ml for thyme essential oil and BHA, respectively. (HP)TLC-bioautographic assay performed with Gram positive and Gram negative bacteria revealed a minimum inhibitory concentration (MIC)values comprised between 0.10 mg/ml (Escherichia coli)and 10.10 mg/ml (for e.g. Pseudomonas aeruginosa), and the fraction mainly characterised by sesquicineole (97.38 percent)as the most involved in antibacterial capacity. Ames test employing Salmonella typhimurium TA98 and TA100 with and without a metabolic activation mixture (S9 mix)demonstrated the absence of mutagenicity of the C. lechleri essential oil between a concentration range of 10?2 and 100 mg/plate. The same results were achieved by Saccharomyces cerevisiae D7 strain assay. An interesting mutagen-protective efficacy was evidenced by a 30 percent and 33 percent revertants reduction of TA98 strain treated with 2-aminoanthracene and nitrofluorene (2 ?g/plate), suggesting, above all, the possibility to employ C. lechleri essential oil as a new flavouring protective ingredient for foods or dietary supplements against potential mutagens formed during cooking and/or processing in general.