Abstract Oligochaetes ( Lumbriculus variegatus ) were exposed to sediment spiked with four 14 C‐polychlorinated alkanes (PCAs) (C 12 H 20 C 16 56% Cl by weight, C 12 H 16 Cl 10 69% Cl, C 16 H 31 Cl 3 35% Cl, and C 16 H 21 Cl 13 69% Cl) to measure bioaccumulation parameters and biotransformation. Chlorinated paraffins are industrial products that consist of thousands of different PCAs. Chlorinated paraffins are hydrophobic (log octanol–water partition coefficients K ow s > 5.0) and are reported to have relatively high concentrations in sediment compared with other persistent organochlorines; however, no data exist on their bioavailability from sediment. The PCAs C 12 H 20 Cl 6 , C 12 H 16 Cl 10 , and C 16 H 31 Cl 3 were readily available to sediment‐ingesting oligochaetes, whereas C 16 H 21 Cl 13 had lower bioavailability. Uptake rates of the C 12 ‐PCAs were greater than the C 16 ‐PCAs, but half‐lives (t ½ s) were greater for the C 16 ‐PCAs (t ½ = 30‐33 d) than for the C 12 ‐PCAs (t ½ = 12‐14 d). Biota–sediment accumulation factors were >1 for C 12 H 20 Cl 6 , C 12 H 16 Cl 10 , and C 16 H 31 Cl 3 , but <1 for C 16 H 21 Cl 13 . Comparison of toluene‐extractable and ‐nonextractable 14 C suggest that PCAs were biotransformed in aerobic sediments and by oligochaetes, and that the susceptibility to degradation in sediments decreases with increasing chlorine content. The relative abundance of individual PCAs may differ between sediment and benthic invertebrates because of differences in the bioaccumulation and degradation of PCAs of varying carbon chain length and chlorine content.