A fiber optic miniprobe (FOMP) system, based on remote fluorometry, has been developed recently for in situ, real-time measurement of solute transport processes in soil. This relatively new FOMP system is now ready to be tested in field applications. In transferring this technique to field soils, we must consider new issues of probe calibration, installation, and protection from the elements, as well as temperature sensitivity of the measurements. In order for the FOMP output light intensity measurements to be converted to fluorescent tracer concentration, an in situ calibration is necessary for each probe. Each step of the conventional calibration method consists of leaching the entire soil sample with several pore volumes of tracer solution. The steady signal measured by the probes at each step is then related to tracer concentration. This procedure works well for typical laboratory soil columns, but is impractical for fiber optic calibration in longer soil columns or in field conditions, due to the large amounts of time and tracer required. As a result, a "point" calibration method has been developed, which consists of injecting standard solutions directly into the small soil volume surrounding the measurement tip of the probe. Comparisons of the conventional leaching method to the injection method showed that the new procedures work well in both silica sand and clay loam soil columns. As a result, the FOMP system was tested in a heterogeneous field soil using the new calibration technique, along with new field materials and methods, including protective housing, installation, and temperature correction. The point injection procedure was successful, and the FOMPs were shown to be capable of in situ, real-time measurements of solute transport processes in a field plot.