This paper presents the results of and conclusions drawn from two experimental studies of low-elevation slant-path scintillation. Part I describes observations made on an 11.2 GHz, 3.3 path over a two and a half year period. Received signal strength and a variety of concurrent meteorological parameters were recorded. The resulting database has enabled the veracity of the 1990 International Telecommunications Union-Radio [(ITU-R)-formerly International Consultative Radio Committee (CCIR)] model to be determined. An interesting discrepancy between the CCIR prediction procedure and the experimental data suggests an as yet unmodeled scintillation mechanism operating in wet summer weather.