In this poster, we report that varying the contact force in force spectroscopy results in a significant shift in DNA unbinding forces, measured from short oligonucleotides using a PicoForce microscope. The contact force between a 30-mer complementary DNA-coated probe and surface was varied from 100 pN to 10 nN, resulting in a significant shift in the most abundant unbinding force measured between the duplex. We also examined the effect of salt concentration on the DNA unbinding force for a range of salt concentrations from 5 mM to 500 mM. Salt ions are necessary to facilitate the hybridization process. Although an increase in salt concentration resulted in facilitating DNA multiple binding events during force spectroscopy measurements, no significant shift in unbinding forces was observed. Our experiment demonstrates that the wide variation in DNA unbinding forces reported in the literature (50–600 pN) for short oligonucleotides can be accounted for by different contact forces used and shows little or no effect by the salt concentration used in those studies.