In recent years, semiconductor quantum dots have been applied with great advantage in a wide range of biological imaging applications. The continuing developments in the synthesis of nanoscale materials and specifically in the area of colloidal semiconductor nanocrystals have created an opportunity to generate a next generation of biological labels with complementary or in some cases enhanced properties compared to colloidal quantum dots. In this paper, we report the development of rod shaped semiconductor nanocrystals (quantum rods) as new fluorescent biological labels. We have engineered biocompatible quantum rods by surface silanization and have applied them for non-specific cell tracking as well as specific cellular targeting. The properties of quantum rods as demonstrated here are enhanced sensitivity and greater resistance for degradation as compared to quantum dots. Quantum rods have many potential applications as biological labels in situations where their properties offer advantages over quantum dots.