Organic field-effect transistors (OFET) based on octamethylenetetrathiafulvalene (OMTTF) and the t-butyl derivative are investigated. The parent OMTTF shows poor transistor performance owing to the flat molecular arrangement, but the t-butyl substitution realizes standing molecular arrangement and high OFET performance. The tetracyanoquinodimethane (TCNQ) complex of OMTTF exhibits n-channel properties despite the strong donor ability of OMTTF.