Oil Country Tubular Goods (OCTG) is a term used to describe the family of steel pipes that are used in the oil and gas industry for construction of wells and hydrocarbon production. The American Petroleum Institute (API) specifies the technical delivery conditions and requirements for OCTG. These requirements include material properties, dimensions, tolerances and allowable defects among others. The tolerances for dimensions and allowable geometrical defects are referred here as geometrical imperfections. This thesis focuses on the impact that these geometrical imperfections have on the strength of OCTG, which is a concern for both casing and tubing designers and tubular manufacturers. Eccentricity between the pipe outside and inside diameter, ovality of the pipe cross-section and lack of longitudinal straightness are the common geometrical imperfections included in the analysis, in addition to a particular case with internal surface wear caused by tool joint friction. The evaluation using the Finite Element Method (FEM) of pipes with and without the geometrical imperfections reveals that the theoretical calculations for onset of yield fail to capture the effect of imperfections under certain loading conditions. The eccentricity and lack of straightness impact the tension and compression strength while the ovality and internal surface wear impact the internal and external pressure strength. A high dependence of the onset of yield on the pipe geometry is identified and characterized in the post-processing of results. Finally, strength reduction factors that take into account the imperfection type, its magnitude, the loading conditions and relevant pipe geometry variables are proposed.