This paper describes a study of Trieste sea level data for the period 1875–1914. Monthly sea level means for 1875–89 and 1901–04 are here reported and analysed for the first time after their original publication. This increases the length of one of the few Mediterranean records spanning more than a century. Trieste data are quality controlled by comparison with those of other stations in the northern Adriatic, and several monthly values that differed from that shown by the reference stations were detected. An explanation for the suspect data is difficult because of the absence of detailed information on the tide gauge operation. The discrepancies probably are due to instrumental problems. The completeness of the data that make up the monthly means does not seem to play a significant role. The addition of data to the previously known record does not affect the long-term linear trend estimate, which turns out to be 0.13±0.01 cm/y for both the old and the updated time series.