This paper describes health monitoring of concrete aerial structures for a light-rail train system. The purpose of the study is to perform structural diagnostics and in-situ inspection for 8 line sections under various climate conditions, and with incremental static loading during construction, and dynamic loading due to moving trains. The field diagnostics include instrumentation on piers, pier caps, bridge girders and decks with electrical strain gages and tilt meters. Initial gage-installation efforts are focused on in-situ temperature developed in bridge decks and rail pads. Some tilt plates are installed early prior to deck construction on piers and beams to study the effects of deck placement such as changes in camber and pier rotation. Temperature gages to measure surface temperatures are installed next to every gage type. A non-contact infrared sensor is also being used to measure surface temperature. Air and wet bulb temperature are recorded with other measurements along with time and weather conditions. At this time, the in-situ temperature gages provide two datums: information about cement heat of hydration, and information about diurnal deck temperatures. Tilt-meter measurements record de-camber of pre-stressed concrete I-beams. Graphs of these measurements show miscellaneous events such as beam replacements on pads, pouring of decks, diaphragms, etc. Material properties and structural behavior are discussed for several aerial structural components.