A precipitated iron catalyst (100 Fe/0.3 Cu/0.8 K) was tested in a fixed-bed reactor and a stirred tank slurry reactor at 250-260 degrees C, 1.48 MPa, 2 Nl g-cat(-1) h(-1), and H-2:CO = 2:3. Two different pretreatment procedures were employed (hydrogen reduction at 250 degrees C and synthesis gas activation at 280 degrees C) in each of the two reactor types. The activity of the hydrogen reduced catalyst was stable with time-on-stream, and it produced more methane and gaseous hydrocarbons than the syngas pretreated catalyst. Secondary reactions (olefin hydrogenation and isomerization) were more pronounced in tests with the hydrogen reduced catalyst. Hydrocarbon distribution shifted toward lower-molecular-weight products with time-on-stream in the stirred tank slurry reactor tests, but the total olefin content of C-2 to C-15 hydrocarbons remained constant during the tests which lasted 300 hours.