Inbred guinea pigs selected for high (IMM/S) respectively low (IMM/R) responsiveness to ovalbumin (OA) as measured by induced respiratory anaphylaxis, were investigated for atopic immune responses of their conjunctival mucosa. IMM/S animals sensitized either by inhalation of OA, or by instillation of antigen into the conjunctival sac, developed regularly an acute ocular inflammatory response to topical (conjunctival) challenge with the allergen. A minimum of 1 microgram OA dropped repeatedly into the conjunctival sac was enough for both ocular and systemic sensitization of the animals, but the minimal dose of effective challenge was considerably higher. In IMM/R animals, ocular hypersensitivity was not achieved by inhalation of OA, but after topical administration of the antigen some of the IMM/R strains could be challenged to ocular anaphylactic responses of the same intensity as observed in IMM/S animals. The conjunctivae of both IMM/S and IMM/R animals could be sensitized passively by intraperitoneal injection of guinea pig sera containing homocytotropic antibodies to OA, but topical administration of such sera had no effect.