Electronic payment systems for wireless devices need to take into account the limited computational and storage ability of such devices. Micropayment schemes seem well suited to this scenario since they are specifically designed for efficient operation. Most micropayment schemes require a digital signature and therefore users must support public key operations and, furthermore, a public key infrastructure must be available. Such schemes are not suitable for current wireless systems since public key technology is not supported. We examine the SVP micropayment scheme which overcomes this problem by using only symmetric key cryptography and relying on tamper resistance. Some limitations are observed in the SVP micropayment scheme and an enhanced scheme is proposed suitable for current generation wireless communications.