Morphology and deformation behavior of samples of iPP homopolymer containing exclusively gamma-modification with only minor traces of alpha-crystals, obtained by isothermal crystallization at high pressure of 200 MPa, were investigated. It was found that the growth of gamma-lamellae is initiated on "seeds" consisting of a spine of single alpha-lamella and several shorter alpha-lamellae branching at the angle of 80 degrees. Epitaxial growth of gamma-lamellae on (010) faces of alpha-parent and daughter lamellae of the seed leads to the formation of immature spherulites, which eventually fill completely the sample volume. The plane-strain and uniaxial compression tests demonstrated higher modulus, higher yield stress and flow stress, yet slightly lower ultimate strain of gamma-iPP as compared to alpha-iPP. During plastic deformation numerous fine shear bands, initiated by the interlamellar shear of the amorphous layers start to develop already at the yield point. Their propagation across the sample causes a limited destruction of gamma-lamellae oriented perpendicularly to the direction of the band. Destroyed fragments of crystallites transform partially into a smectic phase. No gamma-alpha phase transformation was detected. With increasing strain the shear bands multiply and tilt gradually toward the flow direction. Lamellae, already fragmented within shear bands, undergo kinking and rotation, resulting in the formation of a chevron-like lamellar morphology. Simultaneously, a relatively weak one-component crystalline texture is developed. This texture is described by the orientation of c crystallographic axis along the constrained direction, b axis 10-30 degrees away from the loading direction toward the flow direction, and a axis 10-30 degrees away from FD. Both crystalline texture and lamellae orientation are developed due to the activity of the same deformation mechanisms-the interlamellar slip produced by the shear within interlamellar amorphous layers. Activity of any crystallographic deformation mechanism within crystalline component was not detected. The interlamellar amorphous shear appears the primary deformation mechanism of gamma-iPP. The other identified mechanism, gamma-smectic phase transformation, plays a minor, supplementary role in the deformation sequence.