Galvanomagnetic effects have been measured and compared in single‐crystal iron films 0.1 to 5 μ in thickness and in iron whiskers 10 to 500 μ in thickness. Measurements have been made in a temperature range 1° to 300°K and in magnetic fields to 80 kOe, although in this paper we discuss primarily the low‐field negative magnetoresistance observed at helium temperatures. The negative magnetoresistance develops when the mean free path of the electron becomes long. In the case of whiskers with RRR≈1000 the effect can represent a 90% reduction in resistance at 4.2°K, while with films having RRR≈10–50 the effect is reduced to 1%. The negative magnetoresistance in 〈100〉 axial whiskers is very sensitive to measuring current, while the negative magnetoresistance in 〈111〉 axial whiskers is not as sensitive, although both cases show substantial deviations from Ohm's law. Analysis of the longitudinal and transverse data on the films indicates that the reverse galvanomagnetic effect is making a substantial contribution. Hall‐effect measurements have also been made but do not show any anomalous behavior in low fields.