This chapter considers the relationship between private practice and the public good through the lens of an under-examined organizational form: the “private public interest law firm.” This form of practice attempts to marry profit and principle in organizations built around some vision of the public good, and it rejects the conventional understanding of pro bono, which distinguishes between paid work and public service. Our analysis of the trajectory of the private public interest sector suggests that it has grown in scale and complexity over the past quarter century. Its development has been influenced by “pull” and “push” factors: the advent of fee-shifting statutes has provided a significant financial incentive for private practice in areas associated with public interest law, while constraints on nonprofit public interest organizations have prodded some lawyers to enter the private sector in search of greater autonomy. Our preliminary survey of the field suggests that lawyers in private public interest firms generally believe that their core (paid) practices advance the public good and they tend to see pro bono, as conventionally defined, as a modest public-spirited gesture promoted by lawyers whose practice model is much less consistent with the public interest than their own. Although they sometimes accept what are, in effect, pro bono cases with no (or very little) expectation of recovering fees, they do so for reasons that differ from those of their big firm counterparts. The views and practices of lawyers in such firms show that the bar’s definition of pro bono, as unpaid service to clients who cannot pay, is a particular view of professionalism that is more congenial to lawyers in some practice settings than others. We suggest that “lawyering for the good” in the private sector should be understood as a spectrum of market-embedded practices that entail different tradeoffs between professional ideals and economic realities.