An asset management system includes a plurality of assets, a plurality of sensors for determining one or more operating conditions for each of said assets and one or more processors for determining a risk profile for each of the assets over time. The processor is arranged to calculate a risk index value for each asset from the risk profile, the risk index providing a relative indicator of the need for maintenance of an asset. A maintenance queue is established and assets are entered into the queue once the risk index value for that asset matches or exceeds a predetermined threshold value, the position of the asset in the queue being determined based upon the value of its risk index.