Electronic devices based on single crystals of organic semiconductors provide powerful means for studying intrinsic charge-transport phenomena and their fundamental electronic limits(1-4). However, for technological exploitation, it is imperative not to be confined to the tedious growth and cumbersome manipulation of molecular crystals - which generally show notoriously poor mechanical properties - but to be able to process such materials into robust architectures by simple and efficient means. Here, we advance a general route for facile fabrication of thin-film devices from solution. The key beneficial feature of our process - and the principal difference from existing vapour deposition(5-7) and solution-processing schemes(7-10) - is the incorporation of a glass-inducing diluent that enables controlled crystallization from an initial vitreous state of the organic semiconductor, formed in a selected area of the phase diagram of the two constituents. We find that the vitrifying diluent does not adversely affect device performance. Indeed, our environmentally stable, discrete rubrene-based transistors rival amorphous silicon devices, reaching saturated mobilities of up to 0.7 cm(2) V-1 s(-1), ON-OFF ratios of >= 10(6) and subthreshold slopes as steep as 0.5 V per decade. A nearly temperature-independent device mobility, indicative of a high crystalline quality of our solution-processed, rubrene-based films(11), corroborates these findings. Inverter and ring-oscillator structures are also demonstrated.