Several clinical synchrotron facilities for carbon ion-beam therapy were constructed worldwide during the last decade. State-of-the-art at these facilities is a compact room-temperature injector linac operated at about 200 MHz and comprising at least one electron cyclotron resonance (ECR) ion source, a radio-frequency quadrupole linac (RFQ), and an Interdigital H-mode drift tube linac (IH-DTL). Whereas superconducting linacs are favorable for high-duty cycle or cw operation, room-temperature linacs still have advantages for low-duty cycle machines like synchrotron injectors. Recent developments applying higher frequencies and higher gradients as well as more compact RF supplies based on solid state power amplifiers or IOTs may open new options for future injectors. An overview of present injector linacs as well as selected recent developments will be presented.