Self-assembled monolayers were formed by immersing Au(111) surfaces into solutions of benzeneselenol and diphenyl diselenide. Chemisorption of benzeneselenol produced numerous gold islands (20-200 Angstrom in diameter) on the surface and a selenium-containing monolayer with a fundamental repeat unit of(3 root 3 x 2 root 3)R30 degrees. Upon annealing at 60 degrees C in air, these gold islands coalesce to form larger, hexagonal-shaped islands. Chemisorption of diphenyl diselenide is qualitatively similar and upon annealing appears to produce the same surface structures observed with benzeneselenol. These organoselenium-modified surfaces were investigated by scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES).