The short A743 links Lanark with the A70 Ayr-Edinburgh route, which, while signposted Lanark from Edinburgh, actually skirts the town to the south. The road was originally numbered B715 but, later in the 1920s, was the first A7xx road to be given Class I status after the original 1922 classification.
The road starts on Lanark High Street at the A73TOTSO and becomes D1 almost immediately. The A743 is actually carrying eastbound A73 traffic as well here as that road is one-way into the town centre. Just after the road narrows again the B7017 turns off to the right at traffic lights, taking A73 traffic with it, and the A743 continues ahead through the suburbs.
The road soon reaches open country. An industrial estate is passed to the right before the road goes over the Lanark branch line. After being lined by houses for a short distance the road ends at a TOTSO on the A70. Continue ahead for Carstairs and (ultimately) Edinburgh.