Shape indices of roundness, flatness, dissymetry, oblateness, sphericity, and form-ratio derived for pebbles drawn from ten occurrences of conglomerates and boulder beds formed the basis for environmental interpretations obtained by comparison with standard values. Serious inconsistencies emerged, casting doubt on coarse sediment morphometry as a tool for environmental discrimination. Statistical tests were applied in an effort to resolve the problem, but these led only to further problems. Specifically, roundness, sphericity, and oblateness are found to be unreliable for discriminatory purposes, which, with flatness and dissymetry already questioned, brings to five the number of shape measures whose reliability has been called into question. Positive steps are suggested that may help to resolve the problems surrounding the reliability of coarse sediment morphometry for diagnostic purposes.