This paper reports intensity-time signatures of eight impulsive (nearly) pure solar electron (Ee≳45 keV) events observed in interplanetary space in the heliocentric radial range 0.7AU, seven by Mariner V (July--October 1967) and one by Mariner II (November 1962). In six cases, simultaneous solar X ray and Earth-based optical data provide reasonably certain identification of the causative flares. Complementary data on X ray emission and electron angular distributions from Explorer 33 (in a loose Earth orbit) and Explorer 35 (in a lunar orbit) are also cited. In all eight cases the electron signatures exhibit a two-phase structure, an early scatter-free peak [Lin, 1970> having a duration of ≲20 min and a subsequent main phase having a full width at half maximum of several hours. A detailed analysis of each intensity-time signature is described, and the corresponding parameters are tabulated. All main phases are well represented by a three-dimensional, isotropic diffusion equation, although it is puzzling that such a representation can be so empirically successful. The principal results are apparent values of the interplanetary diffusion coefficient D and corresponding values of the mean free path &lgr; between scattering centers for the main phases. Values of &lgr; range from 0.035 to 0.154 AU. The mean of these values is 0.091 (¿0.013) AU and the standard deviation of individual values from the mean is 0.040 AU. This standard deviation exceeds the estimated uncertainty of each determination by a factor of about three and is plausibly attributed to variability of the properties of the interplanetary magnetic field. ¿ 1998 American Geophysical Union