A long-standing ambition in the field of organic electronics has been to harness the self-organizing properties of certain classes of molecules to assemble key device structures without human intervention — the 'bottom up' approach to microelectronics. Single, self-assembled layers of such molecules have been successfully implemented in the form of SAMFETs (self-assembled-monolayer field-effect transistors), but the properties of the devices have been disappointing, largely due to defects in the monolayers and poor electronic coupling within the layers. Smits et al. now show that these limitations can be overcome by chemically designing the component molecules to ensure dense, highly ordered packing. The good electrical performance and high reproducibility of the resulting SAMFETs is demonstrated by combining over 300 of them into a functional integrated circuit. An ambition in the field of organic electronics has been to harness the self-organizing properties of certain classes of molecules to assemble key device structures without human intervention. Single, self-assembled layers of such molecules have been successfully implemented in transistors, but the devices' properties have not been promising, largely due to defects in the monolayers and poor electronic coupling between the molecules within the layers. It is now shown how such limitations can be overcome, by carefully tuning the properties of the molecules through chemical design to ensure dense, highly ordered packing in the self-assembled monolayer. The good electrical performance and high reproducibility of the resulting devices is demonstrated by combining over 300 of them into a functional integrted circuit. Self-assembly—the autonomous organization of components into patterns and structures1—is a promising technology for the mass production of organic electronics. Making integrated circuits using a bottom-up approach involving self-assembling molecules was proposed2 in the 1970s. The basic building block of such an integrated circuit is the self-assembled-monolayer field-effect transistor (SAMFET), where the semiconductor is a monolayer spontaneously formed on the gate dielectric. In the SAMFETs fabricated so far, current modulation has only been observed in submicrometre channels3,4,5, the lack of efficient charge transport in longer channels being due to defects and the limited intermolecular π–π coupling between the molecules in the self-assembled monolayers. Low field-effect carrier mobility, low yield and poor reproducibility have prohibited the realization of bottom-up integrated circuits. Here we demonstrate SAMFETs with long-range intermolecular π–π coupling in the monolayer. We achieve dense packing by using liquid-crystalline molecules consisting of a π-conjugated mesogenic core separated by a long aliphatic chain from a monofunctionalized anchor group. The resulting SAMFETs exhibit a bulk-like carrier mobility, large current modulation and high reproducibility. As a first step towards functional circuits, we combine the SAMFETs into logic gates as inverters; the small parameter spread then allows us to combine the inverters into ring oscillators. We demonstrate real logic functionality by constructing a 15-bit code generator in which hundreds of SAMFETs are addressed simultaneously. Bridging the gap between discrete monolayer transistors and functional self-assembled integrated circuits puts bottom-up electronics in a new perspective.