The self-assembly of several cis-unsaturated carboxylic acids of the structure cis-CH3(CH2)(p-1)CH=CH(CH2)(m-1)-COOH on highly oriented pyrolytic graphite (HOPG) was studied. The impact of the interior cis-CH=CH group and the molecular chain length on their self-assembled structures was considered. Due to the cis conformation of the -HC=CH-group in the interior of these molecules, they display self-assembled structures significantly different from saturated acids with all-trans configurations. As an example of the class of molecules cis-CH3(CH2)(p-1)CH=CH(CH2)(2n-1)COOH (p not similar or equal to 2n) (p = 8, n = 7), cis-CH3(CH2)(7)CH=CH(CH2)(13)COOH self-assembles into two kinds of enantiomer domains with opposite 2-D chirality. Due to the steric restriction of the interior cis-HC=CH group, all chains with acid groups are packed at the same side of a lamella, a head-to-head arrangement which is different from the head-to-tail packing of saturated all-trans acids. However, cis-CH3(CH2)(7)CH=CH(CH2)(8)COOH, considered as one example of the group cis-CH3(CH2)(p-1)-CH=CH(CH2)(2n-2)COOH (p not similar or equal to 2n -1) (p = 8, n = 5), does not form any stable self-assembled domain, consistent with the molecular arrangement model. This difference in self-assembly behavior between cis-CH3(CH2)(p-1)CH=CH(CH2)(2n-1)COOH (p not similar or equal to 2n) and cis-CH3(CH2)(p-1)CH=CHC2n-2COOH (p not similar or equal to 2n - 1) shows an odd-even chain-length effect of cis-CH3(CH2)(p-1)CH=CH(CH2)(m-1)COOH (p not similar or equal to m, m = 2n or 2n - 1). For another category of molecules, cis-unsaturated acids with equal numbers of all-trans carbon atoms on both sides of the cis-CH=CH group, cis-CH3(CH2)(m-1)CH=CH(CH2)(m-1)COOH (m = 2n or 2n -1), display another odd-even effect. cis-CH3(CH2)(7)CH=CH(CH2)(7)COOH, one example of cis-CH3(CH2)(2n-1)-CH=CH(CH2)(2n-1)COOH(n = 4) (n = 4), is predicted to form both an enantiomer and a nonchiral racemic structure, which is in accordance with the experimental observation of its self-assembled monolayer. However, cis-CH3(CH2)(2n-2)CH=CH(CH2)(2n-2)COOH does not form a stable self-assembled domain due to the same steric repulsion as that seen in the cis-CH3(CH2)(7)CH=CH(CH2)(8)COOH structure. These odd-even effects demonstrate that molecular self-assembly can be significantly tailored by slightly changing the molecular chain length.