The design and optimization of spiral inductors on silicon substrates, the related layout issues in integrated circuits, and the effect of the inductor-Q an the performance of radio-frequency (RF) building blocks are discussed. Integrated spiral inductors with inductances of 0.5-100 nH and Q's up to 40 are shown to be feasible in very-large-scale-integration silicon technology. Circuit design aspects, such as a minimum inductor area, the cross talk between inductors, and the effect of a substrate contact on the inductor characteristics are addressed. Important RF building blocks, such as a bandpass filter, low-noise amplifier, and voltage-controlled oscillator are shown to benefit substantially from an improved inductor-Q.