The origins of fiberoptic thermometry, its strengths and limitations and the general characteristics of its commercial applications are discussed. Three classes of measurement systems are considered as commercial: (1) those employing point sensors for measurement of low to intermediate temperatures; (2) those employing point sensors for measurement of intermediate to high temperatures; and (3) those employing distributed sensors. The principal technologies in each class are reviewed and specific applications are then examined. Finally, future developments are suggested.