During summer and autumn 1988, benthic fluxes of nutrients and oxygen were measured in the Bay of Cadiz. The study was carried out using benthic chambers and in addition by determining gradients of nutrient concentration in interstitial water. Fluxes ranged between 13.5–24.3, 3.4–7.8, 6.1–28.4 and (− 99.4)−(− 188.5) mmol m^{− 2} d⁻¹ for NH₄ ⁺ , o-P, SiO₂ and O₂ respectively. These values are far higher than those reported by other authors for locations at similar latitudes. The stoichiometry of O, N and P transference suggest that benthic degradation of principally allochthonous organic matter takes place mainly through anaerobic pathways.