Little data is available on the treatment of patients with advanced non-small-cell lung cancer (NSCLC) in every-day clinical practice. Clinical trials hardly reflect reality due to strict selection criteria and a focus on the treatment line of interest. Thus, we aimed to describe the prevalence of treatment measures in a cohort of unselected patients with advanced NSCLC. From January 2003 to July 2007, we included 416 consecutive NSCLC patients treated at a single institution in this observational study, with a follow-up until August 2008. At each treatment line the time, duration and kind of therapy (drugs used, radiotherapy, surgery), response and time of progression were documented. Of the 405 patients receiving first-line systemic therapy, 52%, 26% and 10% received a second-, third- and fourth-line systemic therapy, while 31%, 40% and 50% of the patients died during or after their first-, second- and third-line therapy, respectively. About 35% of all patients received radiotherapy at any time. About half of the patients with advanced NSCLC undergoing systemic therapy in first-, second- or third-line also receive subsequent therapy. Although this is expected to influence overall survival, previous or further lines are seldom presented in trials in detail and are usually not included in statistical analyses.