This dissertation studies the decision making problems in single period supply chains that face price-sensitive and stochastic demand. We first consider a single-period supply chain consisting of a single supplier and a single retailer with a buy-back contract under a Stackelberg game model, in which the supplier (leader) decides on the wholesale price, and the retailer (follower) responds to determine the retail price and the order quantity. We analytically investigate the decentralized retailer’s optimal decision. The results in the dissertation demonstrate that the retailer has a unique optimal simultaneous decision on the retail price and the order quantity, under a mild restriction on the demand distribution. As it is known that the decentralized supply chain facing price-sensitive random demand cannot be coordinated with a buy-back contract, there exists the chance of making Pareto-improvement for the supply chain. Thus, we propose a scheme for the system to achieve Pareto-improvement. Theoretical analysis suggests that there exists a unique Pareto-equilibrium for the supply chain. In particular, when the Pareto-equilibrium is reached, the supply chain is coordinated.Second, we consider a single-period supply chain with two competing suppliers selling partial-substitute products through a common retailer who faces price-sensitive stochastic demand. While earlier researches often assume that the customs are homogeneous, in this study, by taking their difference in consumption behaviors into consideration, we divide the customers into two categories: those who are price-sensitive and those who are brand-loyal. Under this setting, we investigate the channel coordination issue for this supply chain system. In addition to four traditional contracts, we also explore three sophisticated contracts, each of which combines two traditional contracts, and study the optimal strategies of the retailer under each contract. The results in the dissertation indicate that, amongst the contracts that we have investigated in this dissertation, only a revenue sharing contract and a properly combined buy-back and sales rebate contract can coordinate the supply chain system. All the other contracts studied in this dissertation, including a wholesale price contract, a buy-back contract, a sales rebate contract, a combined buy-back and revenue-sharing contract, a combined revenue-sharing and sales rebate contract, are shown to fail to coordinate the supply chain.Apart from the coordination issues, a great stream of literature studies the decentralized supply chain. We then investigate a decision making problem in the decentralized supply chain system with two competing suppliers and a single retailer under the price-sensitive stochastic demand. We particularly consider a scenario, in which buy-back contracts are employed and each supplier imposes a minimum order quantity requirement on the retailer. In this scenario, the retailer chooses to carry only one or both of the partial-substitute products and makes joint decision on the retail price and the order quantity to optimize her profit. We analytically show that the retailer has a unique optimal strategy.