The solid-state electrical conductivities of a number of ferredoxin model compounds are reported. For one of these compounds, (KFeS 2 ) n , an electron transfer rate for a 25 Å unit is shown to be at least 1 × 10 8 electrons sec -1 . The rate becomes proportionally larger for smaller molecular units. This rapid rate is consistant with a short pipe model for electron transport between two reaction sites. Some of the factors leading to this rapid transfer rate are considered.