Abstract: Monitoring apparatus comprises a support device for receiving a plurality of items to be monitored in an array, each item having a unique machine-readable identifying reference associated therewith, the arrangement being such that the items are movable to different positions in the array; a sensor device for intermittently and repeatedly monitoring each item in the array to monitor changes in a variable associated with each item and to read the reference associated with each item; device for supplying data to the monitored variable and machine-readable reference of each item to a computer, wherein the computer relates the monitored variable to the reference to each item independently of the position of the item in the array.