The Peruvian fauna of aquatic and semiaquatic bugs comprises 233 species, representing 70 genera, 15 tribes, 29 subfamilies, and 16 families. Many of these species (22%) are endemic to the country, while 49% occur in Peru and other South American countries, 21% are found throughout the Neotropics, and 8% are widely distributed in the Americas. These proportions are similar among the three infraorders treated here. There is a slight predominance of Gerromorpha (48%) over Nepomorpha (46%) in Peru, and both are much more speciose than Leptopodomorpha (6%). The same Gerromorpha predominance also occurs in Colombia and Ecuador, whereas Nepomorpha is richer than Gerromorpha in Brazil, Argentina, and Chile. Within Peru, 92% of the species of aquatic and semiaquatic bugs have been recorded from the Atlantic slope, 16% occur in the Pacific slope, and only 2% in the Titicaca slope.