The quiescent and flow-induced crystallization of a poly(ether-block-amide) is studied by means of rheo-optical methods. Both optical microscopy and small angle light scattering have been used. The multiblock copolymer has a microphase-separated structure with an order-disorder transition at 180-185 degrees C, as measured with rheometry and SAXS. The number of nuclei, spherulitic growth rates, and the characteristic time scale for crystallization are compared with that of a polyamide of similar molar mass. For the poly(ether-block-amide) -containing a majority of amide segments-the growth rates of the spherulites during quiescent crystallization are similar for the block copolymer and the homopolymer, even if the spherulitic structures are not the same. When flow is applied, the two materials behave differently. The flow increased the nucleation density in the homopolymer but not in the block copolymer. POLYM. ENG. SCI., 48:2418-2425, 2008. (C) 2008 Society of Plastics Engineers