This paper reviews what is known about sector-based training strategies, to date, including the evaluation evidence, and why they have become so popular with policymakers. The paper also reviews several major challenges to expanding sector-based training strategies while trying to maintain their quality. These challenges include the fact that only workers with strong basic skills and employability are likely to benefit from these strategies; the likely tradeoffs between short- and long-term impacts and between general and more specific training; the difficulties of replicating and scaling the best models; and the uncertain future labor demand. The paper concludes with a number of policy recommendations, both specific and general in nature, in light of the challenges sector-based strategies face.