Under some conditions, time series of the interplanetary magnetic field strength and components have the properties of fractal curves. Magnetic field measurements made near 8.5 AU by Voyager 2 from June 5 to August 24, 1981, were self-similar over time scales from ~20 s to ~3¿105 s, and the fractal dimension of the time series of the strength and components of the magnetic field was D=5/3, corresponding to a power spectrum P(f)~f-5/3. Since the Kolmogorov spectrum for homogeneous, isotropic, stationary turbulence is also f-5/3, the Voyager 2 measurements are consistent with the observation of an inertial range of turbulence extending over approximately four decades in frequency. Interaction regions probably contributed most of the power in this interval. As an example, one interaction region is discussed in which the magnetic field had a fractal dimension D=5/3.