Commercial antibodies are used widely to quantify and localize the alpha1-adrenergic receptor (AR) subtypes, alpha1A, alpha1B, and alpha1D. We tested ten antibodies, from abcam and Santa Cruz, using western blot with heart and brain tissue from wild-type (WT) mice and mice with systemic knockout (KO) of one or all three subtypes. We found that none of the antibodies detected a band in WT that was absent in the appropriate KO or in the KO that was null for all alpha1-ARs (ABDKO). We conclude that the antibodies we tested are not specific for alpha1-ARs. These results raise caution with prior studies using these reagents. For now, competition radioligand binding is the only reliable approach to quantify the alpha1-AR subtype proteins. Receptor protein localization remains a challenge.