Based on the information of the interdisciplinary task force on allergy diagnostics in the metal branch, in 2001, the German Contact Dermatitis Research Group (DKG) compiled two metalworking fluid (MWF) test series with currently and previously used components, respectively. After 2 years of patch testing, we present results obtained with these series, based on data of the Information Network of Departments of Dermatology (IVDK). 251 metalworkers who were patch tested because of suspected MWF dermatitis in 2002 and 2003 were included in this retrospective data analysis. Of these, 206 were tested with the current MWF series and 155 with the historical MWF series. Among the current MWF allergens, monoethanolamine ranked 1st with 11.6% positive reactions. Diethanolamine (3.0%), triethanolamine (1.1%), and diglycolamine (1.9%) elicited positive reactions far less frequently. Allergic reactions to p-aminoazobenzene were frequently observed (6.0%), but the relevance of these reactions is still obscure. Positive reactions to biocides ranged from 4.5% for Bioban CS 1135 to 0.5% for iodopropynyl butylcarbamate and 2-phenoxyethanol. Concomitant reactions to formaldehyde, which caused positive reactions in 3.3%, and formaldehyde releasers occurred to varying extents without conclusive pattern. No positive reactions were seen to dibutyl phthalate, di-2-ethylhexyl phthalate, tricresyl phosphate, isopropyl myristate or benzotriazole. With the historical MWF test series, positive reactions to methyldibromo glutaronitrile (MDBGN) were observed most frequently. However, sensitization via allergen sources other than MWF seems likely, as MDBGN, during the study period, has been one of the most frequent preservative allergens in cosmetics and body care products. Other historical MWF allergens comprised morpholinyl mercaptobenzothiazole (3.3%), benzisothiazolinone (BIT; 2.0%) and Bioban P 1487(1.3%). BIT is currently used in MWF again, so it was shifted to the current MWF test series. As decreasing reaction frequencies to former MWF allergens that are no longer used can be expected, the historical series should be re-evaluated after some years. The test series with current MWF allergens has to be kept up-to-date based on information from industry and to be kept concise by eliminating test substances which never cause positive reactions.