Electron spin resonance (ESR) and electron spin echo modulation (ESEM) spectroscopies have been used to characterize small paramagnetic Ag clusters and their precursors, generated in the interlayer regions of montmorillonite, hectorite, and saponite smectite clays. Samples of days, ion exchanged with Ag+ and solvated with water or methanol, were gamma-irradiated at 77 K and monitored as the temperature was increased, No evidence for cluster formation was found in hydrated clays. However, when solvated with methanol, all three clays are able to stabilize Ag-3(2+) and Ag-4(3+) in interlayer sites. Differences in the behavior of the three clays were observed, particularly in their abilities to stabilize Ag-0 centers formed at 77 K. Montmorillonite is able to stabilize weakly coordinated Ag-0 even at room temperature, whereas Ag-0 is unstable above 200 K in the other two clays. Differences are explained in terms of the structures of the clays.