The present review covers forty-three scientific papers, most from our laboratory, which deal with the synthesis and biological evaluation of a series of condensed benzimidazoles, quinazolines and perimidines. These compounds, containing pseudothiourea as a general structural unit, exhibited considerable biological activities, such as antihypertensive, diuretic anorectic, and thermoregulating effects on animals as well as good herbicidal properties against hydroponieally grown greens.