Mobile environments are characterized by high variability (e.g. variable bandwidth, disconnections, different communication prices) as well as by limited mobile host resources. Such characteristics lead to high rates of transaction failures and variable execution costs. To raise the success rate of transactions and to have a minimal control on resources consumption we claim that both application design and transaction management should be environment aware. This paper proposes an Adaptable Mobile Transaction model (AMT) that allows defining transactions with several execution alternatives associated to a particular context. When an AMT is launched, the appropriate execution alternative is initiated depending on the current environment state. The goal is to adapt transaction execution to context variations. Our model relaxes atomicity and isolation properties but preserves confict-serializability. A specification of the AMTmodel in ACTA (formalism based on the first order logic) is presented. An analytical study shows that using AMTs increases commit probabilities and that it is possible to choose the way transactions will be executed according to their costs.