Bed bugs, Cimex lectularius L., feed on humans, have increased exponentially in the past two decades in many major cities throughout the world, have caused intense infestations, and have become a significant health concern. Improved traps are needed to detect early infestations, to assess control programs, and for control of bed bugs. Carbon dioxide released alone or simultaneously with other attractants into three types of traps at the relatively low rate of 1 ml/min caught significantly more bed bugs than untreated controls in a 183- by 183-cm arena. This finding may enable CO₂ to be used more economically in traps. Three percent ammonium bicarbonate released at a rate of ≤0.03 ml/h also caught significantly more bed bugs than untreated controls. A blend of (E)-2-hexenal and (E)-2-octenal at concentrations of 0.025% or 0.1% each and released at 0.02 ml/h attracted significantly more bed bugs than untreated controls. These findings ought to improve detection of bed bugs.