Cloud computing enables elasticity – rapid provisioning and deprovisioning of computational re-sources. Elasticity allows cloud users to quickly adapt resource allocation to meet changes in theirworkloads. For cloud providers, elasticity complicates capacity management as the amount of re-sources that can be requested by users is unknown and can vary significantly over time. Overbookingtechniques allow providers to increase utilization of their data centers. For safe overbooking, cloudproviders need admission control mechanisms to handle the tradeoff between increased utilization(and revenue), and risk of exhausting resources, potentially resulting in penalty fees and/or lost cus-tomers. We propose a flexible approach (implemented with fuzzy logic programming) to admissioncontrol and the associated risk estimation. Our measures exploit different fuzzy logic operators inorder to model optimistic, realistic, and pessimistic behaviour under uncertainty. An experimen-tal evaluation confirm that our fuzzy admission control approach can significantly increase resourceutilization while minimizing the risk of exceeding the total available capacity.