An integrated circuit is provided with adjustable transistor body bias circuitry and adjustable power supply circuitry. The adjustable circuitry may be used to selectively apply body bias voltages and power supply voltages to blocks of programmable logic, memory blocks, and other circuit blocks on the integrated circuit. The body bias voltages and power supply voltages may be identified by computer aided design tools. The body bias voltages may be used to reduce leakage currents and power consumption when high speed circuit block operation is not required. Reduced power supply voltages may also be used to reduce power consumption when high speed circuit block operation is not required. To ensure optimum switching speeds, circuit blocks for which high-speed performance is critical can be provided with minimal body bias voltage or no body bias and can be provided with maximum power supply levels.