The aim of this randomised controlled trial is to identify the optimal treatment duration with phenoxymethylpenicillin for community-acquired pneumonia diagnosed in general practice. Eligible participants are adults (≥18 years) presenting in general practice with symptoms of an acute LRTI (i.e., acute illness (≤ 21 days) usually with cough and minimum one other symptom such as dyspnea, sputum production, wheezing, chest discomfort or fever) in whom the GP finds it relevant to treat with antibiotics. Consenting patients who meet all the eligibility criteria will be randomised (1:1:1:1:1) to either three, four, five, six or seven days of treatment with phenoxymethylpenicillin 1.2 MIE four times daily.