The present study investigated whether proteome pattern of an oyster Crassostrea hongkongensis could be used as a diagnostic tool for contamination and toxicity of metals/metalloids in a real multiple metal-contaminated estuary. We collected oysters along a pollution gradient from highly contaminated to relatively clean sites. The oysters showed distinct contamination gradients of Cu, Zn and Cd. Proteomic analysis of the oyster gills as one of major metal targets identified a proteome pattern composed of 13 commonly altered proteins in the contaminated oysters. The discovered proteome pattern completely segregated the contaminated from the clean individuals, and the pattern achieved clear classification of the oysters with different contamination levels. Importantly, the integrated changes of gill proteome were linearly related to the integrated contamination of the metal mixtures present in oyster tissues. It is suggested that proteome pattern is a promising diagnostic tool for metal pollution assessment in environmental monitoring programs. (C) 2012 Elsevier B.V. All rights reserved.