The dietary fiber and crude fiber contents of different thallus regions (blade, stipe, and holdfast) in three brown algae (Laminaria japonica, Ecklonia stolonifera, and E. cava) were detennined at different ages, and then compared with one another. On a dry matter basis, the soluble dietary fiber (SDF) content was highest ($10.8{pm}0.5%$) in the holdfast of 2-year old L. japonica, and the insoluble dietary fiber (IDF), total dietary fiber (TDF), and crude fiber (CF) contents were highest in the holdfast of 2-year old E. cava at $44.5{pm}0.7%$, $50.2{pm}0.5%$, $6.8{pm}0.7%$, respectively. The IDF, TDF, and CF contents of these three species were measured in the following order: holdfast > stipe > blade, and the SDF contents of L. japonica exhibited the reverse of this trend. The TDF/CF ratio of 1-year old L. japonica, E. stolonifera, and E. cava was greater than was observed in the corresponding 2-year old samples. This is, to the best of our knowledge, the first report demonstrating that the holdfasts of L. japonica, E. stolonifera, and E. cava are rich in dietary fiber contents, especially IDF, TDF, and CF.