The enzymatic activities of 147 samples of commercially produced Spanish poly¯oral and mono¯oral honeys are reported. Important variations in invertase activity and peroxide accumulation were determined to obtain objective information related to honey quality. Variations from 4.04 (Robinia pseudoacacia) to 25.61 g sucrose hydrolysed per 100 g h À1 (SN) (Castanea sativa) and from 11.31 (Erica vagans) to 45.25 mg H 2 O 2 g À1 h À1 (Hedysarum coronarium) were detected, with a range from 10.57 to 46.2 SN in poly¯oral honeys. Honeys from Erica spp had different invertase activitiesÐ high for E cinerea (18.3 SN) and low for E vagans (8.36 SN). The different heating processes of honey have been evaluated to determine the best treatment for preserving invertase activity. The hydroxymethylfurfural content is not a suf®ciently good indicator of the degree of deterioration of honey. Another objective was to assess the use of invertase activity in honey quality legislation.