  We introduce a noncommutative calculus on the odd-symplectic superspace
$\scri$ of fields and antifields. To this end we have to extend $\scri$ to
$\exscri$ by including an extra anticommuting field $\eta$. As a consequence we
show that the commutator induced on $\exnice\times T^\star(\exnice)$ is
proportional to the antibracket. The $\Delta$-operator is an element of the
quotient space of derivations twisted by the antibracket $A\der$ and $\der$.
The natural measure on $\exscri$ is shown to be invariant under canonical
transformations provided a certain 'wave equation' is satisfied.
