Two strong solid state luminescence peaks, centered at 457 nm and 538 nm, were observed from the newly synthesized ternary [In10S20 - xSex]10- T3 clusters, under excitation by UV radiation (λ = 360 nm). The 457 nm peak is due to the porosity property of T3 clusters. Nevertheless, the 538 nm peak has not been reported for the T3 clusters before. In this letter, we demonstrate that the 538 nm peak is attributed to the trace Se atoms confined in the [In10S20 - xSex]10- clusters. The luminescent output from the ternary [In10S20 - xSex]10- T3 clusters is independent of temperature from 298 K until 77 K. ? 2008 Elsevier B.V. All rights reserved.