Animal studies indicate male-mediated teratogenicity for certain carcinogens/mutagens. Nevertheless, paternal occupational determinants of malformations in humans have been sparsely investigated. Data on male employees at Swedish universities from 1970 to 1989 were linked to the Medical Birth Register. The relationship between major malformations and exposure to laboratory work and to specific laboratory agents/techniques before the third trimester were analyzed using logistic regression. For major malformations, "laboratory work in general" (n = 3237) gave an adjusted odds ratio (OR) of 1.3 (95% CI = 0.8-2.1) and carcinogenic solvent use (n = 2489) of 2.0 (95% CI = 0.8-4.9) around the time of conception. For carcinogenic solvents and neural crest malformations, OR was 4.9 (95% CI =1.5-15.8). In conclusion, the prevalence of congenital malformations was not increased in offspring of males with laboratory work in general (1970-1989). Paternal work with agents such as carcinogens could, however, be of concern.