We present data on the production by neutrinos of a prompt ..mu../sup -/..mu../sup -/ signal with a rate relative to the ..mu../sup -/..mu../sup +/ rate (single charm production) of 0.07 +- 0.04, 0.12 +- 0.03, and 0.12 +- 0.03 for p/sub ..mu../>5, >10, and >15 GeV/c, respectively. The energy dependence of the ratio N/sup pr/ (..mu../sup -/..mu../sup -/)/N(..mu../sup -/) is also presented. Like-sign dimuon data from various experiments are summarized and discussed. Our observed ..mu../sup -/..mu../sup -/ rate is roughly two orders of magnitude larger than that expected from leading-order quantum-chromodynamic calculations of associated charm production.