The use of fiber optic chemical sensors (FOCS) opens new vistas for detecting and quantifying various chemical species and measuring selected physical parameters in both fresh and sea waters. FOCS are optical fibers with either "small chemistry laboratories" or transducers attached to their distal ends. Each FOCS has a chemistry or transducer of its own so that its sensitivity and specificity to a compound or class of compounds, or physical parameter is optimized. The FOCS are flexible and less than

m in diameter making them very suitable for in-situ and in-vivo measurements. Portable, self-contained fluorimeters are used in conjunction with the FOCS to excite the sensor, spectrally sort the return light, and to process and display the data. Various FOCS and fluorimeter combinations have been used to generate performance data on FOCS for pH, temperature, pressure, organic chloride, and carbon dioxide.