This paper presents results from ground-based remote sensing of optical properties of shallow convective clouds over the Nauru ARM site using the technique developed by McFarlane et al. (2002). Herein, the results of a pilot study are presented with analysis of about six months of cloud data. The effective radius re shows large spatial variability, with the frequency of occurrence relatively narrow near the cloud base, and gradually widening aloft. Available column data for LWC and re allow derivation of the pdf of the optical thickness τ. The pdf shows that clouds with τ in the range 5 to 10 are most frequent, but there is a long tail with clouds up to τ = 100. These results are discussed in the context of traditional observations of cloud microstructure using an instrumented aircraft.