The tensile deformation behavior of poly(l-butene) and two of its ethylene copoloymers was studied at room temperature. This was done by investigating true stress-strain curves at constant strain rates, elastic recovery properties, and in-situ WAXS patterns during the deformation process. All samples showed a common rubberlike deformation behavior without necking down. The differential compliance, the recovery properties, and the evolution of the crystallite texture changed simultaneously at well-defined points. The strains at which these points occurred along the true stress-strain remained constants for the different samples despite their different percentage crystallinities. The same strain-controlled deformation behavior was also shown by a series of semicrystalline polymers in previous studies that carried out in our group. The well-defined way that the different samples respond to external stresses complies with our views of a granular substructure of the crystalline lamellae in a semicrystalline polymer as a result of the multistep route they follow during their formation.