Farm productivity in the Peanut Basin of Senegal has been declining over time, requiring strategic interventions to reverse this trend. Using pooled cross-section time-series data and probit and Tobit models, this paper examines factors that influence the decision whether or not to use fertilizer (adoption) and the share of land on which fertilizer is used (intensity) in peanut and millet production. Our results show that the probability of using fertilizer increases where household heads have higher literacy, larger families and larger farms, but decreases where they have off-farm income. Fertilizer use is also positively associated with the amount of rainfall and varies by geographical location. The analysis indicates that both the adoption and the intensity of use of fertilizer by peanut and millet farmers have been declining over the study period 1998–2005. Our findings suggest that focusing on market oriented interventions that motivate farmers to invest in improved agricultural technologies is a sensible policy option.