First, a protocol for increasing the stoichiometry of O-GlcNAc on proteins is given. This is followed by simple techniques for the detection/screening of O-GlcNAc-modified proteins either by immunoblotting or lectin affinity chromatography. Separate protocols verify that the glycan is O-linked GlcNAc. These methods are followed by protocols for more comprehensive analysis of O-GlcNAc modified proteins, including labeling of O-GlcNAc residues with [3H]Gal, and subsequent product analysis. The final two protocols assay for O-GlcNAc transferase and O-GlcNAcase activity, respectively.