The pure rotational spectrum of MnF has been measured in its X(7)Sigma(+) ground state using millimeter/sub-millimeter direct absorption methods. Five and six rotational transitions, respectively, were recorded for this radical in its upsilon = 0 and v = I states in the range 338-630 GHz. MnF was created from SF6 and manganese vapor, produced in a Broida-type oven. The species exhibited a complex pattern where the fine and Mn-55 and F-19 hyperfine structures are intermixed. Rotational, spin-rotation, spin-spin and hyperfine parameters have been determined for MnF. These constants have been interpreted in terms of bonding and electronic structure in metal fluorides. (C) 2003 Elsevier B.V. All rights reserved.