In this paper, we propose an efficient fine-grained access control system for secure Personal Health Records (PHRs) in cloud computing. In this system, the patients have fine-grained access control for their health records. The underlying primitive of this system is a newly designed identity-based conditional proxy re-encryption scheme with chosen-ciphertext security, which is the first of its kind that achieves the highest security level. It is also highly efficient. The public parameters size and also, the private key and ciphertext size are constant and our experimental results indicate that the computational cost does not rely on the message size.