An integrated circuit distributed radio frequency oscillator comprises a semiconductor chip which includes a differential input transmission line, a differential output transmission line and, coupled in parallel between these transmission lines at spaced apart portions, a number of differential amplifier cells with adjustable delay. The output end of the output transmission line is coupled back to the input end of the input transmission line by a feedback link with a pair of on-chip capacitors. The delay introduced by the amplifier cells is variable in response to a tuning voltage applied to a differential tuning input, making the oscillator suitable for use as a distributed VCO in, e.g. a phase-locked loop circuit. The layout of the oscillator on a semiconductor chip includes the series-connected arrangement of the differential transmission lines in a rectilinear spiral path.