Based only on the characteristics of the weapons, the long guns likeliest to be substituted for handguns for either defensive or criminal purposes are about 3 or 4 times as deadly as the handguns currently used in assaults; they are also more accurate. Although it is difficult to assess, the circumstances in which homicides occur would easily permit long guns to be substituted in about 50 to 80 percent of the cases. Since many long guns would be no more expensive than black-market handguns under handgun control, cost would not be much of a deterrent to substitution. If handguns were restricted and long guns left relatively unrestricted, there would seem to be no reason why the majority of violence-prone handgun owners and would-be owners would not substitute long guns. Among defensive owners, fear would be ample motivation to substitute, while among criminal owners, the desire to continue their criminal careers and the advantages of having a firearm would encourage substitution. A handgun-only control policy would save lives only if fewer than 31.8 percent of the violence-prone handgun owners and would-be owners substituted long guns. Based on the analysis of the reasons for firearms ownership, this low percentage seems highly unlikely. A well-enforced permissive licensing system (which has never been attempted) would grant firearms licenses to all adults who wanted them, except those who had been convicted of a violent crime within the past 7 years. A total of 53 footnotes is included.