The Bolivian National Constitution of 2009 prohibits the commercialization of genetically modified organisms, but the decree permitting the unique event of glyphosate resistance was enacted earlier. Herbicide-tolerant (HT) soybean is the only transgenic crop grown by farmers in Bolivia, introduced initially by farmers. This pilot study of smallholders was conducted in the midst of political sensitivities and exceptional weather. Results support the hypotheses that adoption of HT soybeans is associated with use of less toxic herbicides and that Mennonite farmers are a primary source of HT seed and related information. The association that subsidized non-HT growers is the major source for conventional seed. Using a control function approach to address endogeneity and selection bias with censored outcome variables, we find that HT soybean adoption has a large, positive impact on household off-farm income and is positively related to off-farm work of the second major contributor to soybean production (wife or children of household head), but not that of the first (household head).