Isoflavone (IFL) intake may provide numerous health benefits, but IFL bioavailability differences among soya foods remains uncertain. Urinary IFL excretion (UIE) was shown to provide a reliable surrogate for systemic IFL exposure and therefore can be used as a measure of ‘apparent bioavailability’ (AB). We investigated the AB of IFL in fourteen healthy adults, consuming two liquid and two solid soya foods in a crossover designed study. Volunteers consumed the foods with a self-selected breakfast, which was kept identical for all four soya items (soya nuts, soya milk, soya protein bar and soya protein powder drink in water; average 23·7 mg IFL, 88–96 % glycosides, by HPLC analysis) and collected all urine up to 26 h. Liquid foods showed initially higher UIE values than solid foods, but this difference was considerably reduced or disappeared entirely after 24–26 h. Conclusive AB results were obtained only after 24–26 h; earlier collections were not reliable. At 26 h, adjusted UIE values for daidzein (DE) were 20 μmol in the milk and bar and 17 μmol for the nut and powder; urinary genistein excretion was the highest in the milk group (10 μmol) followed by the nut, bar (both 6 μmol) and powder groups (5 μmol); the UIE for glycitein was the highest for bars (4 μmol), followed by powder and nuts (3 μmol), and milk (2 μmol). DE makes the largest contribution to urinary total IFL. The AB of IFL was found to be variable depending on the analyte and soya food consumed.