A commonly encountered issue in process industry is concerned with the detection of plant-wide oscillations. In this paper, a new visualization tool termed as the power spectral correlation map (PSCMAP) is proposed for this purpose. The proposed colour map is based on a new measure defined as the power spectral correlation index (PSCI). A simple clustering algorithm is developed to group blocks of variables with similar spectral shapes. The combined visualization tool is shown to be simple, effective and powerful in collecting variables with common frequency-domain behaviour in a multivariate process. The potential of the combined technique is illustrated by an application to two industrial processes, (i) a simulated pulp and paper process and (ii) a SE Asia refinery. © 2005 Elsevier Ltd. All rights reserved.