A time series of quasi-MSL at Brest was computed as part of the thesis work of Nicholas Pouvreau (University of La Rochelle, 2008). This series starts during the 18th century, much earlier than the true-MSL series from 1807 available from the PSMSL. One can employ a MHW time series as quasi-MSL if the large nodal signals in the record can be removed and if an adjustment can be made for average MHW-MSL. An implicit assumption is that low-frequency sea level signals of interest manifest themselves similarly in both MHW and MSL. Two methods were used to do this. In the first method, the differences between MHW (slightly smoothed as described by Wöppelmann et al., 2008, Geophysical Research Letters) and MSL for the post-1807 period, when both quantities were available, were parameterised by a nodal sinusoidal term plus an offset. This parameterisation was then applied to the MHW data from the 18th century in order to derive estimates of MSL. In the second method, a tidal prediction based on best knowledge of the tide at Brest was subtracted from each individual measured high water level, with the annual mean residuals defined to be quasi-MSL. The two methods yielded almost identical results and so only those from the second method are given here. The file shows lines with year, quasi-MSL (adjusted-MHW in cm with respect to the Zero Hydrographique) and the number of days of data available in the year. The file contains a short section of years from the beginning of the 18th century which must be used with caution. The same data can also be accessed via the electronic supplement (http://www.ocean-sci.net/6/185/2010/os-6-185-2010-supplement.zip) to Woodworth et al. (2010, Ocean Science). Discussion of this time series, together with other long sea level records, may be found in Woodworth et al. (2011, Surveys in Geophysics) and Long et al. (2014, Earth and Planetary Science Letters).