We investigate the solar-cycle dependence of the occurrence rate in the solar wind of regions with abnormally low proton temperatures during the years 1965 to 1990. To identify such regions, we compare the observed temperature with the temperature expected from the proton temperature-solar wind speed correlation found in ‘normal’ solar wind. The occurrence rate of abnormally low temperature plasma is correlated with solar activity levels and in particular with the rate of coronal mass ejections
(CMEs) at the Sun. The low temperature regions show higher than chance associations with other signatures of ejecta in the solar wind. However abnormally low temperature plasma is not be a unique signature of ejecta since around 30% of the regions identified are related to encounters with the heliospheric plasma sheet, and the occurrence rate for these events depends more on the tilt angle of the heliospheric current sheet than on the CME rate.