The lamellar structures in uniaxially drawn films of miscible crystalline/crystalline polymer blends of poly(vinylidene fluoride) (PVDF) and poly(3-hydroxybutyrate) (PHB) were investigated by static and time-resolved measurements of small-angle X-ray scattering (SAXS). Intense SAXS in the low angle range of the meridian was interpreted as originating from the interlamellar inclusion structure, in which the PHB chains were included between the lamellae of PVDF. The interlamellar inclusion was induced for the uniaxially drawn films of PVDF/PHB = 30/70 blend with a draw ratio (DR) of 2.8-4.5, whereas the lamellae of the PVDF and PHB components were mutually excluded from each other forming their own lamellar stacks (interlamellar exclusion) in the blend with a higher DR (5.0-5.7). When the highly drawn film with the interlamellar exclusion structure was heat treated at 154165 C, the interlamellar inclusion structure was partially induced by the heat treatment. The time-resolved SAXS measurements indicated that the interlamellar inclusion structure was developed by melting and recrystallization of PVDF during the heat treatment. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 381-392, 2009