Solid-state track recorders (SSTR) of muscovite mica have provided absolute fission rates and fission ratios for 235U and 238U in ZPR-6, Assembly 5. The results agree well with diffusion theory and satisfactorily with radiochemical fission rate measurements. However, comparisons with fission chamber measurements reveal some differences, which can be attributed to the perturbing influence of the fission counter itself. Due to the high sensitivity of the SSTR method, measurements were readily extended into the blanket region of the assembly. Simplicity, reliability, and the wide sensitivity range make SSTR measurements an unusually powerful method for fission rate studies in low-power reactors.