The abundance of cellular proteins is determined largely by the rate of transcription and translation coupled with the stability of individual proteins. Although we know a great deal about global transcript abundance, little is known about global protein stability. We present a highly parallel multiplexing strategy to monitor protein turnover on a global scale by coupling flow cytometry with microarray technology to track the stability of individual proteins within a complex mixture. We demonstrated the feasibility of this approach by measuring the stability of ∼8000 human proteins and identifying proteasome substrates. The technology provides a general platform for proteome-scale analysis of protein turnover under various physiological and disease conditions.