– 7 – 2. Sample Selection $^{1}$available at the Infra-Red Science Archive http://irsa.ipac.caltech.edu/data/SPITZER/C2D/ $^{2}$available at http://irsa.ipac.caltech.edu /data /SPITZER/C2D/doc opacity holes. The structure of this paper is as follows. Our sample selection criteria are presented in § 2, while our observations and data reduction techniques are described in § 3. We present our results on disk masses, accretion rates, and multiplicity in § 4. In § 5, we discuss the properties of our transition disk sample and compare them to those of non-transition objects. We also discuss the likely origins of the inner holes of individual targets and the implications of our results for disk evolution. Finally, a summary of our results and conclusions is presented in § 6. We drew our sample from the 297 Young Stellar Object Candidates (YSOc) in the Ophiuchus catalog 1 of the Cores to Disks (Evans et al. 2003) Spitzer Legacy Project. For a description of the Cores to Disks data products, see Evans et al. (2007) $^{2}$. In particular, we selected all the targets meeting the following criteria: a. Have Spitzer colors [3.6]-[4.5] < 0.25. These YSOc are objects with small or no near-IR excess (see Figure 1). The lack of a [3.6] - [4.5] color excess in our targets is inconsistent with an optically thick disk extending inward to the dust sublimation radius, and therefore indicates the presence of an inner opacity hole. The presence of this inner opacity hole is the defining feature we intend to capture in our sample. This feature is present in ∼ 21% of the YSOc in Ophiuchus as our first criterion selects 63 of them (out of 297). b. Have Spitzer colors [3.6]-[24] > 1.5. We apply this criterion to ensure all our targets have very significant excesses. It removes the 10 YSOc with smallest 24 µ m excess (i.e., 1.5 > [3.6]-[24] > 1.0) and leaves 53 targets.