New clinical tools that aid in the early diagnosis of ovarian malignancies will significantly help reduce mortality and improve current long-term survival rates. The objective of the work presented here was to identify ovarian tumor specific single stranded DNA probes termed aptamers that bind to cell surface structures with high affinity and specificity. First I identified aptamers using a random screening protocol known as Cell-SELEX that bind and internalize to target cells. All aptamers identified demonstrate unique binding kinetics and internalized by the endocytic pathway. Next I assessed the internalization kinetics of identified aptamers when used to label the surface of polymeric organic nanoparticles. I was able to demonstrate that the high specificity exhibited by aptamers promotes localization and uptake of tethered nanoparticles by specific cell populations. Finally a preliminary pilot study looking at the in vivo stability of aptamers and their ability to promote retention and honing of nanoparticles at tumors was conducted. The experiments described here demonstrate the effective combinatorial use of aptamer and nanoparticle technologies for the direct targeting of tumor cell populations.