We have measured the sticking probabilities for sputtered Ag and Au atoms incident on oxidized aluminum surfaces as a function of the areal density of deposited atoms. For Ag sputtered by 200 keV Ar ions, we found a sticking probability at zero coverage of k(0) = 0.46 ± 0.20. For very high coverages, we found k(n > 10^(17)at./cm^2) = 0.80 ± 0.20. For Au sputtered by 200 keV Ar ions, w found k(0) = 0.92 ± 0.08 and k(n > 10^(17)at./cm^2) = 0.80 ± 0.03. For Au sputtered by 200 keV Xe ions, values of k(0) = 0.98 ± and k(n > 10^(17)at./cm^2) = 0.89 ± 0.03 were obtained. In all cases, the sticking probability varied noticeably for densities between o and twenty monolayers. For Au, a maximum value near 1 was observed in this region while for Ag, the sticking probability exhibited a minimum of approximately 35%. Some possible explanations for these results are offered and the implications for collection-type sputtering experiments are discussed.