Seabream embryos (Sparus aurata) were exposed to various concentrations (0.05 to 10.0 mg L-1) of different homologues (C10 to C14) and a commercial mixture of linear alkylbenzene sulfonates (LAS), as well as one long-chain degradation intermediate, sulfophenyl carboxylic acid (SPC C11), to study the acute toxicity of these compounds. LAS homologues of higher chain length (C13 and C14) were proved to be more toxic than shorter species (C10, C11, and C12). LAS C13 and C14 provoked 100% lethality at concentrations of 0.1-0.25 mg L-1. On the other hand, shorter LAS homologues (chain length) did not produce any lethal effect at concentrations up to 5 mg L-1. In this work, results on the toxicity of a long-chain degradation intermediate of LAS, SPC C11, are presented. This compound did not produce any mortality at all the concentration ranges chosen.