“Inorganic fertilizer is one of a handful of agricultural technologies that have immense potential for raising the productivity of poor smallholders, enabling them to increase income, accumulate assets, and set themselves economically on a pathway out of poverty. This paper presents the results of a broad study of fertilizer supply to smallholder farmers in Tanzania that was done to assess whether the taxes (explicit or implicit) that are applied at various points along the fertilizer importation and marketing chain or the absence of key public goods and services reduces the access that smallholder farmers have to fertilizer. The study involved a review of the literature of fertilizer supply, demand, and use; interviews with key participants in fertilizer importation and marketing in Tanzania; and two surveys—one with farmers and the other with input suppliers—in three farming areas where more fertilizer is used than is the norm for the country as a whole.