Gold nanorods have unusually strong absorption in near infrared, which can be utilized for an optical imaging with nanocolloids. The feasibility of photoacoustic imaging of inflammatory responses using bioconjugated gold nanorods is demonstrated. To target the stimulated cells, gold nanorods were conjugated to anti-intercellular adhesion molecule-1 (ICAM-1) which binds to cell surfaces over expressing ICAM-1. A monolayer of stimulated endothelial cells labeled with bioconjugated gold nanorods was scanned using a high frequency transducer. Photoacoustic images differentiated inflamed cells from control cells and matched well with fluorescence images. This technology may permit identification of critical inflammation sites such as blood vessels.