The present study reports on the composition of volatiles of most grape marcs (bagaceiras) commercially available in Portugal. These spirits, which are a valuable by-product of the winemaking industry, are obtained via steam-distillation of grape pomace after storage under anaerobic conditions for a given period of time. An impetus for this research is the increasingly strict European legal standards pertaining to the levels of health hazard volatile compounds (e.g., methanol) and the lack of comprehensive studies on this topic for Portuguese bagaceiras. Assays were performed by gas/liquid chromatography for alcohols (methanol, 2-butanol, 1-propanol, 2-methyl-propanol, allylic alcohol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, hexanol, trans-3-hexenol, cis-3-hexenol, trans-2-hexenol, and 2-phenyl-ethanol), carboxylic acids (isobutyric, isovaleric, hexanoic, octanoic, decanoic, and dodecanoic acids), esters (ethyl acetate, ethyl butyrate, isoamyl acetate, ethyl hexanoate, hexyl acetate, ethyl lactate, ethyl octanoate, ethyl decanoate, diethyl succinate, 2-phenyl-ethyl-acetate, and ethyl dodecanoate), as well as for an aldehyde (ethanal) and its acetal (diethoxy-1-1-ethane). The average values obtained for Portuguese bagaceiras (and the corresponding ranges) were comparable with corresponding values for grape pomaces manufactured in other Mediterranean countries (viz. Spain). The mean contents of methanol were ca. 3389 mg/liter, a value below the accepted threshold of 5000 mg/liter for a 50% (v/v) ethanol-containing grape marc (EC Regulation No. 1576/89).