BACKGROUND: Aligned with the international call for universal coverage of affordable and quality health care, the government of Tajikistan is undertaking reforms of its health system aiming amongst others at reducing the out-of-pocket expenditures (OPE) of patients seeking care. Household surveys were conducted in 2005, 2007, 2008 and 2011 to explore the scale and determinants of OPE of users in four district of Tajikistan, where health care is legally free of charge at the primary level. METHODS: Using the data from four cross-sectional household surveys conducted between 2005 and 2011, time trends in OPE for consultation fees, drugs and transport costs of adult users of family medicine services were analysed. To investigate differences along the economic status, an asset index was constructed using principal component analysis. RESULTS: Adjusted for inflation, OPE for primary care have substantially increased in the period 2005 to 2011. While the proportion of patients reporting the payment of informal consultation fees to providers and their amount were constant over time, the proportion of patients reporting expenditures for drugs has increased, and the median amounts have doubled from 5.3 US$ to 10.7 US$. Thus, the expenditures on medicine represent the biggest financial burden for patients accessing a primary care facility. Regression models showed that in 2011 patients from the most remote district with spread-out villages reported significant higher expenditures on medicine. Besides the steady increase in the median amount for OPE, the proportion of patients reporting making an informal payment to their care provider showed great variations across district of residence (between 20% and 73%) and economic status (between 33% among the 'worst-off' group and 68% among the 'better-off' group). CONCLUSIONS: In a context of limited governmental funds allocated to health and financing reforms aiming to improve financial access to primary care, the present paper indicates that in Tajikistan OPE - especially in relation to expenditures for drugs - have increased over time, and vary substantially across geographical areas and economic status. The fact that better-off households report disbursing more and in higher proportions hints towards a discrimination along the capacity to pay from providers. Increased public investments in the health sector, incentives for family doctors to provide PHC services free of charge and a strengthened drug control and supply system are necessary strategies to improve access of patients to services.