By-products of lipoperoxidation reactions may be associated with the genesis or the progression of several diseases as arteriosclerosis, diabetes and cancer, among many others. Acrolein, at first a widely distributed environmental pollutant, is currently known as a compound capable of being generated as a result of metabolic reactions within biological systems, highly toxic and the most electrophilic of the alpha, beta-unsaturated aldehydes formed during lipoperoxidation. In the present study: 1. The separation of acrolein and malondialdehyde was achieved at alkaline pH with the use of high voltage capillary electrophoresis in uncoated fused-silica capillaries. 2. It was demonstrated how the oxidation of fatty acids (arachidonic/linoleic) with ozone generates, in dose-dependent form, acrolein as one of the by-products of the lipoperoxidation process. The oxidation of open human erythrocyte membranes with ozone also generated acrolein. 3. After aldolic condensation, aldol-acrolein derivative has a positive reaction with 2-thiobarbituric acid (TBA) and shows a maximum absorption at 498 nm. This novel characteristic is used in its identification after the separation of the by-products. 4. It is possible to suggest that in the classic reaction of the denominated thiobarbituric acid reactive substances (TBARS), when used as an indicator of the degree of peroxidation in biological systems, a portion of acrolein could be present but dwarfed by the TBA-MDA adduct.