Objectives This paper used national survey data to investigate ‘hardcore’ smoking as predicted by the ‘hardening hypothesis’, and to examine the relationship between ‘hardcore’ smoking and socioeconomic status (SES). Methods Analyses were performed using data from four waves of the Australian National Drug Strategy Household Survey between 2001 and 2010, a large national survey with a sample size of approximately 24 000 participants per wave. The primary outcome variable was ‘hardcore’ smoking, comprised of the variables: ‘no quit attempt in past 12 months’; ‘no plan to quit’; and smoking more than 15 cigarettes per day. The main predictor variables used were SES assessed by the Socio-Economic Indexes for Areas (SEIFA), and survey wave. Other sociodemographic variables were also examined. Results Overall, ‘hardcore’ smoking remained stable from 2001 to 2010. However, ‘hardcore’ smoking declined among high-SES smokers (from 1.8% to 1.0%), but not among low-SES smokers (around 3.4%). ‘Hardcore’ smoking was strongly associated with SEIFA quintile (p<0.001). There was a significant interaction effect between top and bottom SEIFA quintiles and wave (p=0.025), with a decline in ‘hardcore’ smoking measures over the four waves among those in the top two SEIFA quintiles, with odds in 2010 of 0.39 (95% CI 0.17 to 0.87; p=0.012), down from 0.64 (95% CI 0.50 to 0.82; p<0.001) in 2001, while ‘hardcore’ smoking remained stable among those in the bottom two SEIFA quintiles. Conclusions The results from high SES smokers suggest ‘hardcore’ smokers are able to quit, but outcomes among low-SES smokers are less encouraging.