The Atacama Cosmology Telescope (ACT) aims to measure the Cosmic Microwave Background (CMB) temperature anisotropies on arcminute scales. The primary receiver for ACT is the Millimeter Bolometer ArrayCamera (MBAC). The MBAC is comprised of three 32×32 transition edge sensor (TES) bolometer arrays, eachobserving the sky with an independent set of band-defining filters. The MBAC arrays will be the largest pop-updetector arrays fielded, and among the largest TES arrays built. Prior to its assembly into an array and installationinto the MBAC, a column of 32 bolometers is tested at ~ 0.4 K in a quick-turn-around dip probe. Inthis paper we describe the properties of the ACT bolometers as revealed by data from those tests, emphasizinga characterization that accounts for both the complex impedance and the noise as a function of frequency. Copyright 2008 Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.