Sjögren-Larsson syndrome (SLS) is an autosomal recessive disorder associated with reduced activity of the fatty alcohol: NAD+ oxidoreductase complex (FAO). Recent studies indicate that SLS patients are specifically deficient in the fatty aldehyde dehydrogenase (FALDH) component of FAO. To investigate the possibility of carrier detection for SLS, FAO and FALDH activities were measured in cultured skin fibroblasts from normal controls, obligate SLS heterozygotes, and SLS homozygotes using the 18-carbon substrates octadecanol and octadecanal. Three of 11 heterozygotes for SLS had FAO activities that were within the normal range; the other 8 SLS heterozygotes had FAO activities below normal. In contrast, fibroblast FALDH activity was more effective than FAO in discriminating SLS heterozygotes from normal controls. FALDH activity (nmol min-1 (mg protein)-1) in normal controls was 8.54 +/- 1.16 (mean +/- SD; range 6.95-10.77; n = 12) and in SLS heterozygotes was 5.12 +/- 1.31 (range 3.28-6.96; n = 11), or 60 +/- 15% of mean normal activity. One SLS heterozygote had an FALDH activity within the lower range of normal; this heterozygote had an FAO activity below normal. None of the SLS heterozygotes had an FAO or FALDH activity that was in the range of that measured in SLS homozygotes. These results indicate that measurement of FAO and FALDH activities in cultured skin fibroblasts using 18-carbon substrates is useful for SLS carrier detection.