When Havarti cheeses were made from milk concentrated 5-fold using ultrafiltration (UF) and with a direct vat set type starter containing Streptococcus lactis, Str. cremoris, Leuconostoc cremoris and Str. lactis subsp. diacetilactis (i.e. a BD-type starter) their colour, texture, body, and flavour were equal to those of traditionally produced Havarti. The somewhat slower flavour development was associated with a retarded breakdown of protein. Although αs1-casein was almost completely broken down in Havarti cheese made with the ultrafiltration method (UF Havarti) and traditional cheeses after 120 d of storage, degradation of β-casein was retarded in UF Havarti. Rennet contents and numbers of starter organisms were similar in the two types of cheese and thus could not explain the difference in ripening rate. Str. lactis subsp. diacetilactis was dominant in both UF and traditional Havarti cheeses when the BD-type starter was used. By varying the composition of the starter, large variations in the bacterial composition and citrate fermentation in UF Havarti cheeses were obtained. The BD-type starter gave the best organoleptic quality.