In full and partial vertical profiles of the electric field in thunderstorms during the Severe Thunderstorm Electrification and Precipitation Study in 2000, we find evidence for inverted-polarity electrical structures in the convective region of thunderstorms. The evidence consists of polarities opposite from normal (1) in the peaks in the profile of the vertical component of the electric field, Ez, and (2) in the vertical sequence of inferred charges. In storms that possibly are inverted in polarity, the lowest peak in Ez inside the cloud is negative, followed by a positive peak farther up. Near storm top, the uppermost peak is negative, and the uppermost inferred charge is positive. The sounding data do not conclusively prove that inverted-polarity thunderstorms exist, but they support it. If additional data corroborate that such storms do exist, it will require modification of at least some aspects of our conceptual models of storm electrification.