Ben-kida and ben-saalga are popular pearl-millet-based fermented gruels in Burkina Faso. A survey of 318 households in Ouagadougou (Burkina Faso) showed that they are often used as complementary food for young children. Pearl millet and gruels, sampled in 48 production units, were analysed for proximate composition, factors reducing nutrient bioavailability (phytate, insoluble fibres and iron-binding phenolic compounds), alpha-galactosides, sugars, total lactic acid and d-lactic acid, zinc and iron contents. The effects of processing of pearl millet into fermented gruel are discussed. Both positive effects (e.g. a decrease in factors reducing nutrient bioavailability or alpha-galactosides) and undesirable effects (e.g. considerable lipid, protein, iron and zinc losses) were observed. Lactic acid was produced during processing and d(-)-lactate was detected in all samples. The gruels had very low energy density, even after addition of sugar, and low lipid, protein and mineral contents, well below recommendations for complementary foods.