This chapter contains sections titled: Introduction Column Length Column Length and Efficiency/Resolution Column Length and Retention Column Length and Pressure Column Length and Bleed Column Length and Cost Selecting Column Length Column Diameter Column Diameter and Efficiency/Resolution Column Diameter and Retention Column Diameter and Pressure Column Diameter and Bleed Column Diameter and Capacity Column Diameter and Carrier Gas Volume Column Diameter and Injector Efficiency Column Diameter and Breakage Column Diameter and Cost Selecting Column Diameter Column Film Thickness Column Film Thickness and Retention Column Film Thickness and Efficiency/Resolution Column Film Thickness and Capacity Column Film Thickness and Bleed Column Film Thickness and Inertness Selecting Column Film Thickness Manipulating Multiple Column Dimensions