An important limitation in broadcast disk environments is the low bandwidth available for clients to communicate with servers. Whereas advanced applications in such environments do need transaction processing capabilities, given the asymmetric communication bandwidth, we show that serializability is too restrictive in such environments and hence propose a weaker alternative. Specifically, this paper considers the execution of updates under transactional semantics in broadcast disk environments, and develops a weaker correctness criterion. While this is applicable to transaction processing in general, this paper describes mechanisms to achieve this criterion in broadcast disk environments. We show that read-only transactions need not contact the server and can just read consistent data “off the air” without, for example, obtaining locks. Update transactions, however, need to validate their updates at the server.