The vacuum ultraviolet pulsed field ionization-photoelectron spectra of supersonically cooled cis-2-butene (cis-CH3CH=CHCH3) have been measured in the photon energy range of 73 560-75 460 cm(-1). Using the ab initio theoretical rotational constants of cis-CH3CH=CHCH3 and its cation (cis-CH3CH=CHCH3+) and a semiempirical simulation scheme, we have obtained a good fit of the origin vibrational band with partially resolved contours of rotational branches. After taking into account the Stark shift, the ionization energy of cis-CH3CH=CHCH3 is determined to be 73 595.0+/-1.5 cm(-1). Guided by ab initio vibrational frequency calculations, we have also assigned the vibrational bands observed for cis-CH3CH=CHCH3+ in its ground state.