In this paper, we have examined the inflation rates in the Group of Seven countries, investigating issues such as the existence of unit roots, structural breaks, fractional integration and potential non-linearities using a fractional dependence (FD) approach based on Chebyshev polynomials in time. This robust FD approach allows one to test for persistence as well as non-linearity of the series. We first tested for stationarity and structural breaks using classical approaches and observed inconclusive results with regard to the stationarity levels of the series. Using Bai-Perron tests, we actually confirmed significant structural breaks, even up to five, in each of the inflation series. However, noting that structural breaks are significantly related to fractional differentiation, this latter approach was also conducted. Here, we observed that the estimates of the differencing parameter were quite stable across time, and evidence of unit roots was found in the cases of the UK, Canada, France, Japan and the USA; for Germany, we found some evidence of mean reversion, while estimates of d above 1 were found in the case of Italy. On the other hand, non-linear deterministic trends were clearly rejected in all cases. ‡ Asymmetry is a property explaining unequal movements of asset prices (stocks, inflation, oil prices, exchange rates, etc.) between equilibrium state to 'up' market and 'down' market to equilibrium state. There are quite a number of papers on linear unit root testing inflation rates. Starting with Lai [3] who applied the modified Dickey-Fuller (DF) unit root test of Park and Fuller [4], testing nonstationarity in the inflation rates of the Group of Seven (G7) countries, he concluded that inflation rates were stationary. Cook [5] also found stationarity for the US inflation rates when he applied the DF [6, 7] test. Charemza et al. [8] considered inflation rates for a selected group of 93 countries, applying the augmented DF (ADF, [6,7]) tests, and found nonstationarity of the inflation series. Because of the different sample sizes considered in the aforementioned papers, the authors have obtained contradictory results.Structural breaks may affect the stationarity level of the time series [9]. § Zivot and Andrews [10] proposed a unit root test that selects the breakpoint endogenously from the data. This test has been extended to include the case of two break points in both the level and the trend series [11]. Multiple structural breaks tests have been proposed in Bai and Perron [12,13]. Caporale and Paxton [14] investigated stationarity of the inflation rates for five Latin American countries using the ADF unit root test and the unit root test with multiple structural breaks of Bai and Perron [12,13]. These authors found stationarity for three countries with the ADF tests, whereas the unit root test with structural breaks pointed to stationarity for all five inflation series.Some studies have thought of inflation as a dynamic non-linear process, and in this case, non-linear approaches have been conducte...