Chapter 4 is an extensive study of runaway slave advertisements that mention that a slave speaks Dutch. For this chapter, I have compiled a database of 487 enslaved persons, coded by year of flight, name, age, Dutch language ability, name of master, county, and original source. I demonstrate that runaway slave advertisements in New York City and environs plateaued in the period 1760–1800, but peaked later in the Hudson Valley, with exceptional growth in the 1790s and 1800s. The data provide evidence for the persistence of the Dutch language in New York and New Jersey and contribute to a picture of Dutch-speaking slaves presenting a sharp economic challenge to the institution of slavery. By the 1790s, Dutch-speaking slaves were running away at a rate of at least 1 per 500 per year. For Dutch slave owners, this meant a significant loss of capital and, moreover, a risk on their remaining slave capital. Runaway slaves tended to be prime working-age males, and the loss of the best field workers frustrated New York Dutch farmers. The pressure of runaway activity also lowered the value of retained slaves and made New York slavery more costly in general. Runaways put pressure on slaveholders to manumit their slaves, extracting the most labor possible from them before agreeing to let them go.