This paper analyzes firms' motivation to use vertical restraints and the welfare effects of such restraints in a market where oligopolies exist a upstream and sown-stream sectors. We find that both motivation and welfare effects are dependent on the substitutability between goods. Without any regulation, the manufactures adopt exclusive dealing strategy when substitutability is very large, other-wise they adopt resale price maintenance. To attain the social optimal outcome, we suggest the following rule. If substitutability is very small, no intervention is necessary. If the level of substitutability is in the intermediate range resale price maintenance should be prohibited. If substitutability is very large, both resale price maintenance and exclusive dealing should be prohibited.