During the past decade, donor funding for health interventions in Kenya and other African countries has risen sharply. Focused on high-profile diseases such as HIV/AIDS, these funds create islands of intervention in a sea of under-resourced public health services. This paper draws on ethnographic research conducted in HIV clinics and in a public hospital to examine how health workers experience and reflect upon the juxtaposition of ‘global’ medicine with ‘local’ medicine. We show that health workers face an uneven playing field. High-prestige jobs are available in HIV research and treatment, funded by donors, while other diseases and health issues receive less attention. Outside HIV clinics, patient's access to medicines and laboratory tests is expensive, and diagnostic equipment is unreliable. Clinicians must tailor their decisions about treatment to the available medical technologies, medicines and resources. How do health workers reflect on working in these environments and how do their experiences influence professional ambitions and commitments?