N-Succinimidyl 3-[211At]astato-2, 4-dimethoxybenzoate (SADMB) was prepared from a trialkylstannyl precursor in about 70-75% yield. With either trimethyl or tri-n-butylstannyl precursor, no temporal effect was found in the astatodestannylation yield. However, the methyl analog gave slightly better yield which was found to be not statistically significant. A monoclonal antibody (MAb) fragment, Mel-14 F(ab')2, could be labeled using SADMB in 28% coupling efficiency. The specific binding of this labeled fragment to tumor homogenates in vitro was 61.0 +/- 0.5% (62.8 +/- 0.9% for the 131I labeled fragment). Paired-label tissue distribution in normal mice showed similar uptake of 131I and 211 At in many tissues. However, by 14.5 h selectivity of spleen, lungs and stomach for Mel-14 F(ab')2 labeled with 211At compared to 131I was 4.1, 3.8 and 6.4, respectively.