1. INTRODUCTION

2. OBSERVATIONAL DATA: THE SLOAN DIGITAL SKY SURVEY

3. SIMULATIONS
3.1. N-body Simulation and Substructure
3.2. Identifying Galaxies with Halos
3.3. Millennium Simulation
3.4. The Two-Point Correlation Function

4. THE COUNTS-IN-CYLINDERS ENVIRONMENT STATISTIC
4.1. General Description
4.2. Sample Variance
4.3. Companions as a Function of Host Halo Mass and Halo Occupation

5. RESULTS
5.1. Comparing the Models to the SDSS

6. COLOR MODELING
6.1. Color Modeling
6.2. Varying the Vmax Cut
6.3. Isolated Galaxies

7. CONCLUSIONS