Nonsmall cell lung cancer (NSCLC) presenting with miliary intrapulmonary carcinomatosis (MIPC) is rare. We investigated the clinical characteristics and epidermal growth factor receptor (EGFR) mutation rate of NSCLC patients with MIPC at initial diagnosis. From June 2004 to December 2008, we screened newly diagnosed NSCLC patients for MIPC using image-based criteria. We recorded clinical data and analysed EGFR mutation status. For comparison, we collected specimens from stage IV NSCLC patients without MIPC tested for EGFR mutations from April 2001 to November 2008. From 3,612 NSCLC patients, 85 patients with MIPC at initial diagnosis were identified; 81 had adenocarcinoma. Of the 85 patients, 60 had specimen sequencing to detect EGFR mutation; 42 (70%) were positive. Compared with 673 stage IV patients without MIPC, patients with MIPC had higher EGFR mutation rate (p=0.036); even male smokers had a high EGFR mutation rate (91%). Multivariate analysis of prognostic factors for overall survival of the 85 patients with MIPC revealed that adenocarcinoma, absence of extrapulmonary metastasis and having EGFR mutation were associated with longer overall survival. NSCLC patients with MIPC at initial diagnosis had higher rates of adenocarcinoma and EGFR mutation. EGFR tyrosine kinase inhibition may be the treatment of choice for NSCLC patients with MIPC at initial diagnosis among Asians.