Recently, there has been some discussion on this list about ongoing research on the role of unsafePerformIO, lazy IO and evaluation strategies. Within our research group at JWG-University Frankfurt some work has been done concerning the development of a non-deterministic call-by-need lambda calculus FUNDIO as a semantic basis for HasFuse, a modified implementation of the Glasgow Haskell Compiler which compiles Haskell programs using 'unsafePerformIO' in a 'safe' way, i.e. deploys only those optimizations that have been proven correct w.r.t. FUNDIO. In this context, experience with GHC's implementation has shown up that if compiled with ghc -O0 -fno-do-lambda-eta-expansion while avoiding INLINE-pragmas, 'most' uses of unsafePerfomIO are 'safe' in the sense of FUNDIO's contextual equivalence. For further details, downloads of papers and sources, please refer to the project WWW page http://www.ki.informatik.uni-frankfurt.de/research/diamond The results of FUNDIO show how evaluation may be interleaved with direct-call IO. In particular not only (\xs -> let z = length xs in "Hello World\n") _|_ = "Hello World\n" is a valid equation in FUNDIO, but also for an arbitrary expression t which may involve direct-call IO the equation (\xs -> let z = length xs in "Hello World\n") t = "Hello World\n" holds. Furthermore, the investigations indicate that some kind of optimistic evaluation is possible, i.e. the expression t above could be evaluated as long as no IO in t is executed. Hence, a demand-driven style for IO could be achieved. Matthias Mann JWG-University Frankfurt